The microscope is basically an instrument for magnifying the appearance of a small object. The commonest form of simple microscope is the ordinary "magnifying-glass" consisting usually of a single biconvex lens. While it is possible to construct simple microscopes of great power, these are extremely difficult to use. More effective are the compound microscopes where a real image is formed by a set of lenses (the objective) and viewed through a second set (the eyepiece). In its various forms, the compound microscope has today become an essential tool in research and practical fields. It is possible to distinguish two main periods in the history of microscopy.

The Period of the Early Microscopists (1590-1833)

The compound microscope was probably invented in about 1590 by the Dutch spectacle maker Zacharias Janssen. Mention should also be made of Galileo Galilei who in 1610 constructed a microscope which "magnified 50,000 times, making a fly as big as a hen, or a mite the size of a pea". The first applied microscopist of note was Robert Hooke (1635-1703) who in 1665 published his Micrographia containing a description of his microscope and many illustrations of many of his microscopy observations. An important contemporary was the Italian physiologist Marcello Malpighi (1628-1694) whose discoveries in microscopic anatomy upset ancient medical beliefs setting the course for modern physiology and histology. Among Malpighi's many discoveries were his observations of the microscopic components of the liver, brain, kidneys, spleen, bone, and the inner, or what came to be known as the Malpighian, layer of the skin. He was the first to discover red blood corpuscles and to show that they gave blood its colour. He also identified the taste buds and described the chick embryo, the development of the silkworm, and the structure of plants. Malpighi believed that living material was composed of minute glands that separated or mixed the body fluids. Although he misunderstood the microscopic functions of organs, he set the stage for cell theory and histology.

Another great microscopist of this period was the Dutch draper Anthony van Leeuwenhoek, who with the aid of simple microscopes made many discoveries which he announced from 1673 onwards, including that of bacteria (1676). The 17th-century invention of the compound microscope led to the development of microscopic anatomy, which is divided into histology, the study of tissues, and cytology, the study of cells. The study of the microscopic structure of animals and plants flourished during the 17th century, though many great anatomists of the period were reluctant to accept microscopic anatomy as part of their science.

The progress in microscopic research was hampered by very bad chromatic aberration of the early microscopes. The invention on the achromatic lens in 1757 opened the way to colour-free objectives, and in 1830 Joseph Jackson Lister (1786-1869) published a paper entitled "On the improvement of compound microscopes" wherein he described the construction of achromatic-aplanatic objectives for the microscope. By the mid-19th century very good objectives became available which with improved eyepieces gave a sharply defined image on a wide flat field.

The period of acceptance of microscopy as a tool (1833 to date)

Microscopic anatomy developed rapidly in the 19th century. During the second half of the century many basic facts about the fine structure of organisms were discovered, largely as a result of greatly improved optical microscopes and of new methods that made cells and tissues easy to study with this instrument. The method of microtomy, the cutting of tissue into thin, practically transparent slices, was perfected by the Czech physiologist Johannes Evangelista Purkinje. Microtomy was rendered incomparably more valuable by the application to the tissue slices of various types of dyes and stains that make it much easier to see various parts of the cell. In 1878 the German scientist Ernst Abbe (1840-1905) developed the homogenous oil immersion objective which allowed greater resolution with higher magnifications resulting in a large number of discoveries in the medical field especially in the field of micro-organisms.

Bacteria were first observed by Anthony van Leeuwenhoek with the aid of the simple microscope. He reported his discovery to the Royal Society of London in 1683, but the science of bacteriology was not firmly established until the middle of the 19th century. Dyeing or staining bacterial specimens or cultures was introduced in 1871 by the German pathologist Karl Weigert and has greatly helped the bacteriologist in identifying and observing bacteria under the microscope. The first systematic classification of bacteria was published in 1872 by the German biologist Ferdinand J. Cohn, who placed them in the plant kingdom. In 1876 Robert Koch, who had devised the method of inoculating bacteria directly into nutrient media as a means of studying them, found that a bacterium was the cause of the disease anthrax. Other significant developments in bacteriology were the discoveries of the organisms causing glanders (1862), relapsing fever (1868), typhoid fever (1880), tetanus (1885), tuberculosis (1890), plague (1894), bacillary dysentery (1898), syphilis (1905), and tularemia (1912).

Knowledge of microscopic anatomy was greatly expanded during the 20th century as a result of the development of microscopes that provided much greater resolution and magnification than had conventional instruments, thus revealing formerly unclear or invisible detail; and expanded laboratory techniques helped facilitate observation. The ultraviolet microscope allows the observer to see more because the wavelengths of its probing rays are shorter than those of visible light (the resolving power of a microscope is inversely proportional to the wavelength of the light used). It also is used to emphasise particular details through selective absorption of certain ultraviolet wavelengths. The electron microscope gives even greater magnification and resolution. These tools have opened up formerly unexplored fields of anatomical investigation. Other modern microscopes have made visible unstained and living materials that would be invisible under the conventional microscope. Two examples are the phase-contrast microscope and the interference microscope. Through utilisation of ordinary light beams, both these instruments differentiate parts of living, unstained cells [1].

Microscopy in Malta

There is as yet no evidence that any experiments or observations using the technique of microscopy had been performed in Malta prior to the 19th century. The employment of the microscope in clinical medicine was apparently first advocated in Malta by Dr. Costantine Schinas, Professor of Medicine at the University, for the analysis of the solid constituents of urine as early as 1838. Dr. Schinas reproduced a paper from a French publication in the local medical journal which he edited [2]. Dr. John Davy of the British General Military Hospital during his stay in Malta between 1828 and 1835 is known to have had in his laboratory a microscope with an object lens of one-eight inch focal length constructed by the "excellent maker Mr. Ross" who was one of the foremost microscope makers at the time [3]. The microscope had become so well known by 1853 that the Governor donated one to the Literary Cabinet of Zebbug Village [4].

In his journal, Dr. Schinas called attention to the limitations of microscopic examination of blood stains for medico-legal purposes, and reproduced the criticisms levied in France against a French medical expert who claimed to be able to distinguish the sex, age and hair colour of an individual from studying his/her blood [5]. The role of the microscope in the study of blood was reviewed by Dr. F.L. Gravagna, Dr. T. Chetcuti and Dr. G.G. Aquilina in June 1841. The review discussed whether one could distinguish the blood of one species from another on the basis of the microscopic characters of the red blood corpuscles according to the description given by William Hewson (1739-1774). The review also included discussion regarding the role of chemical methods to distinguish the animal species to which the blood belonged [6]. The usefulness of microscopy and spectroscopy in the use of medico-legal identification of human blood remained controversial, though these techniques were used in a murder case which appeared before the Maltese Criminal Court on 4th June 1869. The three medical experts examined the accused trousers which contained stains which they claimed were human blood stains. These results were contested by Dr. G. Gulia, Professor of Legal Medicine, in 1872 when he wrote that the biological sciences had not yet attained a sufficient degree of development to establish beyond doubt the origin of blood stains, quoting medico-legal works by English, German and French authors. Dr. Gulia's opinion was confirmed by Prof. J.D. Macdonald of the Netley Medical School. Dr. Gulia also supported his opinions by carrying out experiments wherein he examined for several months desiccated blood spots from various animals without success in identifying the species [7].

In 1871 Dr. G. Gulia reported his personal experience in detecting for clinical purposes the presence of spermatozoa in urine in a case of a male suffering from a suprapubic fistula, and of finding uric acid crystal in the urine of a woman suffering from eclampsia [8]. He commented that microscopy had not yet become sufficiently widespread among Maltese clinicians, even though in many instances microscopy was essential to enable a correct diagnosis to be made. He advocated more extensive use of the instrument by general practitioners and the Central Hospital for examination of urine and sputum. He recommended the book by H. Frey The Microscope and Microscopic Technology published in 1873 [9].

Dr. Gulia's observations were not surprising in view of the fact that microscopic examination was generally a neglected field of study during medical training, though examination papers in anatomy dated to 1883 include questions on Histology [10]. In 1887 a new statute promulgated by the University of Malta increased the number of professorships in the Faculty of Medicine to six, including a Professor of Descriptive Anatomy, History and Pathological Anatomy. Final year students were required to perform laboratory work in chemistry, pathology and microscopy [11]. In August 1890 an extensive collection of microscopic slides showing the main known pathological bacteria was acquired by the University and placed at the disposal of medical students and practitioners [12]. In March 1900, the clinical staff of the Central Hospital (Floriana) proposed the appointment of a pathologist to the hospital and the creation of a post of Professor of Pathological Anatomy. This suggestion was approved and Prof. Carmelo Samut (who occupied the Chair of Anatomy since 1894) was appointed to these posts in 1901. This appointment allowed the setting up of the hospital laboratory creating new facilities for more intensive training of medical students in the chemical, bacteriological and microscopic examination of pathological specimens [13]. Examination papers on Descriptive Anatomy in 1917 also included questions relating to history and microbiology [14]. Prof. C. Samut retired in January 1920. The University Council decided that anatomy and pathology should be taught by different persons, and two separate appointments were made. The Professor of Pathology was also responsible for the teaching of the newly established course in bacteriology [15].

Bacteriological studies in Malta had an early beginning culminating in as number of bacteriological observations and discoveries. In 1884 Sir David Bruce, just graduated from Edinburgh was assigned to the Army Station Hospital in Malta where British soldiers suffering from Malta Fever were cared for. Encouraged by his wife, who was a brilliant microscopist, Bruce set himself the task to identify the causative agent for the disease. He carried out a post-mortem examination on a fatal case and prepared microscopy paraffin sections on a Cambridge rocking microtome of the spleen. These sections were then stained with watery methylene blue and by Gram's method, and on examination using the homogenous 1/12in. oil immersion objective (developed in 1878) and an Abbe condenser (developed in 1872) an "enormous numbers of single micrococci were seen scattered through the tissues". Whilst on leave, Bruce showed his sections to Dr. Sims Woodhead, pathologist to the Edinburgh Royal Infirmary, Together with the government analyst Dr. G. Caruana Scicluna, Bruce prepared a paraffin section from the spleen from another fatal case and cultured the micrococcus responsible for undulant fever. Bruce went on to prove its causal role by isolating it from splenic cultures from seven other fatal cases, and by animal experiments [16]. In 1904 a commission of enquiry was set up by the Admiralty, War Office and the Civil Government of Malta. The Commission performed a number of experiments, but the most valuable contribution to the Report published in 1905 was that by Sir Themistocles Zammit of the Malta Board of Health, who showed that goats' milk was the main source of infection. In the same year as the discovery of Brucella melitensis (1886), Bruce and his Maltese co-worker Dr. G. Caruana Scicluna cultivated and detected Koch's comma spirillum in the evacuations of cholera victims confirming that cholera was not due to a miasma but was infective in origin [17]. While microscopy was apparently an established tool in investigations relating to infectious disease in Malta by 1886, the situation was not so in Gozo since aetiological and pathological investigations during an epidemic of meningococcal meningitis did not include microscopic examination [18]. In 1892, Dr. M.L. Hughes identified the typhoid bacillus in all the fatal cases of typhoid [19].

Microscopic examination of organs removed at autopsy was definitely carried out at the Military General Hospital (Valletta) in 1860 and probably earlier [20]. At the Central Hospital, microscopic examination of surgical specimens were being performed by the pathologist at least by 1891. The first two laparotomies in Malta was performed by the gynaecologist Prof. G.B. Schembri in 1891. Histological examination of the excised tumours performed by Dr. C. Mifsud showed these tumours to be a cystic adenoma of the ovary and a fuso-cellular sarcoma infiltrating omentum [21].

The twentieth century in Malta saw an increasing dependence on microscopic examination of body fluids and organs to assist in the diagnosis of clinical condition. The use of the microscope was further extended to veterinary medicine. In 1924 the Medical & Health Laboratory received for examination a total of 1560 samples of swabs, smears, sputa, spleen puncture, faeces, ect, form the Loch and Isolation Hospitals. The Veterinary surgeon further submitted seven smears for microscopic examination [22]. During the two years 1929-30, the Pathologist and Bacteriologist employed at the Central Hospital (Floriana) dealt with 674 complete histological examinations of blood, 35 blood cultures, and 91 blood samples examined for parasites; 99 urerthral/vaginal swabs, 195 nasal swabs for leprosy bacilli, and 50 nasal/eye/ear/ throat swabs; 565 sputa samples, 4996 urine samples, and 224 faecal samples; 163 samples of effusions and cerebrospinal fluid; and 1333 samples of hair examined for parasites. Only 209 tissue sections were studied histologically [23].

Microscopy has also been used in other non-medical fields such as metallography and petrography even in Malta. During the nineteenth century in Malta, a series of petrographic studies were carried out on Maltese rocks. Sir John Murray of the "Challenger Expedition" prepared and examined a number of sections of the various layers of Maltese rock stratigraphy and examined these microscopically. These studies confirmed that Maltese rocks were sedimenatary limestones deposited under water. The microscopic organisms identified in the various types of rock suggested that the sediments were laid down in waters of varying depths. Further microscopic study of the Maltese Blue Clay horizon were carried out by John H. Cooke in 1892, while microscopic examination of a fossil extracted from globigerina limestone was performed by Mr. N. Tagliaferro in 1893 who showed this fossil to be the outer layer of a tree-trunk [24].

The "toy" developed by the sixteenth century spectacle maker has now become an essential tool in medicine and other fields of science, not only for laboratory research, but also to aid clinical diagnosis and medico-legal studies.

REFERENCES

1. G.W. White: Introduction to microscopy. Butterworhs, London, 1966, p.1-6; Microsoft (R) Encarta..Microsoft Corporation, U.S.A., 1994

2. L'Ape Melitensis, September 1838, 1(1):25

3. P. Cassar: Physiological and pathological research at the General Military Hospital of Valletta, Malta in the early Nineteenth century. Medi-Scope, 1986, 9:29

4. L'Ordine, 27 May 1853, p.4093

5. L'Ape Melitensis, October 1838, 1(2):132

6. Il Filologo Maltese, 17 June 1841, p.45

7. Il Barth, 20 April 1872, p.136; 8 March 1872, p.109-114

8. Il Barth, 20 April 1872, p.131; 16 October 1871, p.47

9. Il Barth, 9 March 1872, p.109; 22 July 1873, p.318; 15 November 1873, p.334

10. J.L. Pace: The history of the School of Anatomy in Malta . R.U.M., Malta, 1974, p.17, plate 28

11. Statute of the University of Malta, Malta, 1887

12. La Rivista Medica, 1890, i:1

13. Letters to Government: 10th April 1895 to 31st March 1903 . fols.406,590,626,826. Medical & Health Archives [manuscript], Malta: In P. Cassar: Medical History of Malta. Wellcome Historical Medical Libr.: London, 1964, p.460-461

14. J.l. Pace, 1974, op. cit. note 10, p.17, plate 29

15. Statute of the University of Malta, Malta, 1921

16. D. Bruce: Note on the Discovery of a Micro-organism in Malta Fever. Practitioner, 1887, 39:161-170; D. Bruce: The Micrococcus of Malta Fever. Practitioner, 1888, 40:241-249; W.D. Foster: A history of Medical Bacteriology and Immunology . Heinemann: London, 1970, p.88-90

17. S.L. Pisani: Report on the Cholera Epidemic in the year 1887. Malta, 1888, p.6,18

18. C. Savona-Ventura: An Outbreak of Cerebrospinal Fever in a 19th century British Mediterranean Naval base. J. R. Army Med Corps, 1994, 140:155-158

19. M.L. Hughes: The Natural History of certain fevers occurring in the Mediterranean. The Mediterranean Naturalist, 1892, ii:299; iii:325

20. J.A. Marston, Report on Fever (Malta). Army Medical Department. Medical Report for 1861. London, 1863, p.513

21. La Rivista Medica, 15 January 1891, p.2; V. Vella: Due Casi di sezione addominale seguiti da guarigione. Rivista di Ostetricia e Ginecologia, Torino, 1891, reprint +3p.; C. Manche: Nota sul trattamento incruento dell'epitelioma palpebrale. Rome, 1909, p.5; Letters to Genernment: 1st April 1903 to 10th April 1909. fol.137, Medical & Health Archives [manuscript], Malta. In P. Cassar, op. cit. note 13, p.539

22. A. Sultana: Report on the Working of the Laboratory for the year 1924. In: Report on the Health of the Maltese Islands during 1924 (A. Critien). Malta Government Gazette Supllement , 2 October 1925, no.xlv, appendix I, p.30-31

23. F. Mercieca: Report on the Charitable Institution in Maltafor the financial year 1930-31. Reports on the Workings of Government Departments during the financial year 1930-31. Government Printing office, Malta, 1932, section R, p.3-4

24. J. Murray: The Maltese Islands with special reference to their geological structure. Scotish Geographical Magazine , 1890, 6:449; J.H. Cooke: The Marls and Clays of the Maltese Islands. Quart. J. Geol. Soc., 1893, 49:117-128; N. Tagliaferro: The Mediterranean Naturalist, June 1893 IN: J.H. Cooke: Notes on the Globigerina Limestones of the Maltese Islands. Geol. Mag., 1896, 3:504