Page:Encyclopædia Britannica, Ninth Edition, v. 24.djvu/865

Rh ZOOLOGY 815 ilarvey tnd the- Italian chool. [alpighi irtLeeu- enliock. rists rsus iinal- lists. ments should be reconsidered. Anatomy and physiology should be re-united and subdivided as follows, (1) physi ology with anatomy in relation to physiology, (2) anatomy in relation to surgery and medical diagnosis, the former being a science, the latter a piece of technical training in rule of thumb. Physiological anatomy or anatomical physiology has its beginnings in Aristotle and other observers of antiquity. The later Greece-Roman and the Arabian physicians carried on the traditional knowledge and added to it. Galen dominated the Middle Ages. The modern development begins with Harvey and with the Italian school in which he studied. Its great names are Fabricius of Acquapendente (1537-1619), Vesalius (1514-1564), Eustachius (c. 1500- 1574), Riolan (1577-1657), Severino (1580-1656). The history of the discovery of the circulation of the blood and of the controversies connected with it gives an interesting and sufficient presentation of the anatomico-physiological knowledge of the period (see HARVEY). The foundation of the scientific academies and the records of their publica tions furnish thenceforward a picture of the progress in this study. As an early anatomist Willis (1621-1675), professor of physic in Oxford, deserves notice for his work on the anatomy of the human brain, the plates for which were drawn by young Christopher Wren, the prodigy of Oxford common-rooms, who later built St Paul s Cathedral. The Royal Society, in its early days when Wren was a fellow, met at Gresham College whenever the professor of physic there could obtain a human body for dissection, and amongst its earliest records are the memoirs of Tyson on the anatomy of the Chimpanzee and the experiments on transfusion of blood, extirpation of the spleen, and such like inquiries. Marcello Malpighi (1628-1694) and Anton van Leeu- wenhoek (1632-1723) were the first to introduce the microscope into anatomical research. Malpighi first used the injection of blood-vessels on a large scale, and more over is to be credited with having first conceived that there is a definite relation of the structure of lower kinds of animals to that of higher and more elaborate kinds, and that this relation is one of gradual transition, so that lower animals are not to be regarded as isolated and arbi trary existences, but are really simpler exhibitions of the same kind of structure and mechanism which occurs in higher animals. It is this conception which later de veloped into the theory of an actual transmutative deve lopment of lower into higher organisms. Leeuwenhoek discovered the red blood corpuscles of Vertebrates, saw the circulation in the capillaries of the Frog s foot, de scribed the fibrillar structure and cross-striping of muscular fibre, the tubular structure of dentine, the scales of the epidermis, the fibres of the lens, and the spermatozoa, these last having been independently discovered at Leyden in 1677 by Ludwig Ham of Stettin. The spermatozoa were regarded by the &quot; animalculists &quot; as the fully formed but minute young which had to be received in the egg, in order to be nourished and increase in size, and were hailed as a decisive blow to Harvey s doctrine of epigenesis and his dictum &quot;omne vivum ex ovo.&quot; Albrecht von Haller was the champion of the so-called &quot; evolutionists &quot; in the 18th century, better called &quot; pra3 formation ists.&quot; Haller wrote, &quot; There is no such thing as development ! No part of the animal body is made before another ; all are simul taneously created.&quot; A corollary of this doctrine was that the germ contains the germs of the next generation, and these of the next, and so ad injlnitum. It was calcu lated that Eve at her creation thus contained within her 200,000 millions of human germs. This was the view of the &quot; ovists,&quot; who regarded the egg as the true germ, whilst the &quot; animalculists,&quot; who regarded the spermatozoon as the essential germ, would have substituted Adam for Eve in the above calculation. These fanciful conceptions containing as they do a share of important truth were opposed by Caspar Friedrich Wolff, who in his doctorate dissertation (1759) maintained that the germ is a struc tureless particle, and acquires its structure by &quot; epigenesis &quot; or gradual development. Wolff has proved to be nearer the truth than Haller ; but modern conceptions as to the molecular structure of the egg-protoplasm point to a com plexity as great as that imagined by the evolutionists. Later it was maintained that the spermatozoa are parasitic animalcules, and this view prevailed for 150 years, so that in the Physiology of Johann Miiller (1842) we read, &quot;Whether the spermatozoa are parasitic animalcules or living parts of the animal in which they occur cannot at present be stated with certainty.&quot; Physiology in the 1 8th century could only proceed by Von means of inferences from purely anatomical observation, Haller. aided by imaginative conceptions which had no real basis. The explanation of the processes of life in the animal body was waiting for that progress in the knowledge of physics and chemistry which at last arrived, and gave a new im pulse to investigation. Albrecht von Haller (1708-1777) was the first to apply experimental methods to the deter mination of the functions of the various organs made known by anatomists, and from him we may trace a bi furcation in the tendencies of medical men who occupied themselves with the study of the structure and functions of the animal organism. The one class proceeded more and more in the direction of comparative anatomy, the other in the direction of exact analysis and measurement of both the structure and properties of the organs of Ver tebrate animals allied to man and of man himself. John Hunter (1728-1793) is the most striking figure of The two this epoch in the relation of medicine to general zoological Hunters, progress ; the preservation of his museum in Lincoln s Inn Fields, London, by the combined action of the state and the Royal College of Surgeons, is an abiding record of the historical progress of biological science. Hunter col lected, dissected, and described not only higher but lower animals, with the view of arriving at a knowledge of the function of organs by the most extensive and systematic survey of their modifications in all kinds of animals. His purpose was that of the physiologist and medical man, but he made great contributions to the general knowledge of animal structure. The same class of investigations, when taken up by Cuvier from the point of view of systematic zoology and morphology, led to a reconstruction of classi fication and laid the foundation of anatomical zoology. Hunter was the younger brother of William Hunter, who also formed an important museum, still preserved in Glas gow. Hunter classified the organs of animals into those which subserve the preservation of the individual, those which subserve the preservation of the species, and those which are the means of relation with the outer world, and he arranged his museum of dissections and preparations on this plan. The great progress of chemistry at the end of the 18th Rela- and the beginning of the 19th century was followed by an tions of application of chemical laws and chemical methods to the *^ study of animal life. Curiously enough, as showing how 20 ology. deeply interwoven are the various lines of scientific progress, Priestley in his discovery of oxygen was as much concerned in the study of a chlorophyll-bearing Protozoan, Euglcna viridis, as in that of the red oxide of mercury ; and the interest in &quot; vital spirits &quot; as a physiological factor was an important stimulus to those researches which produced modern chemical knowledge. The purely anatomical side of physiological progress is marked in the beginning of the 19th century by the work