XVI THE HISTORY OF ZOOLOGY 669 



immense body of facts, many of them singularly accurate, others 

 as curiously incorrect, a circumstance -which no one will wonder 

 at who, with all modern resources at his elbow, has tried to 

 break fresh ground in any department of Zoology. Although he 

 propounds no definite system of classification, he clearly recognises 

 many of the more important animal groups, or, as he calls them, 

 '' genera." Vertebrata, for instance, are spoken of as animals with 

 blood (evaifia) and Invertebrates as animals without blood 

 [avaiiio), colourless blood not being recognised as such. Among 

 animals with blood are included Viviparous Quadrupeds (Mam- 

 mals), Birds, Oviparous Quadrupeds (Reptiles and Amphibians), 

 Cetaceans, and Fishes: among bloodless forms, Malakia or soft 

 animals (Cephalopods), JMLalacostraca or soft animals with shells 

 (the higher Crustaceans), Entoma (Insects, Arachnids, Myriapods, 

 and the higher Worms), and Ostracodermata or shelled animals 

 (Echinoderms, Cirripedes, Pelecypods, Gastropods, and Tunicates). 

 Starfishes, Medusae and Sponges are also referred to. 



In the then existing state of knowledge it was impossible that 

 even so profound a philosopher as Aristotle could erect a science 

 of Zoology. No standard of nomenclature was established ; there 

 was no clear idea of what constitutes a species : in matters of 

 structure, no distinction was drawn between nerves and tendons : 

 in physiology the vessels and tendons were looked upon as the 

 organs of movement, the muscles being considered as mere packing. 

 Obviously, anything like real progress was barred by ignorance of 

 animal structure and fimction, and it was absolutely necessary 

 that exact anatomical knowledge should precede anything ap- 

 proaching to successful generalisation. 



It is, therefore, hardly to be wondered at that, up to the time 

 of Ray, scientific Zoology owes more to those anatomists and 

 physiologists whose main object was to advance the study of 

 Medicine, than to the naturalists in the ordinary sense of the word. 

 With the exception of the works of G-alen (born A.D. 130), which 

 contain numerous observations on the anatomy of Mammals, 

 anatomy, as well as Zoology in the broad sense, was practically 

 at a standstill from the time of Aristotle to the sixteenth century, 

 when Vesalius, by his observations, chiefly on the human subject, 

 raised anatomy to a degree of accuracy hitherto undreamt of; and 

 Goiter, Bellonius, and Fabricius ab Aquapendente resumed 

 the study of comparative anatomy, dormant since Aristotle. 

 Somewhat later— in 1645— Severino published his Zootomia 

 democretcea, the first book devoted exclusively to the general 

 subject of comparative anatomy. 



During the same period the general knowledge of animals was 

 increasing, and a distinct epoch is marked by the learned, and, for 

 the time, exhaustive Historia animalium of Conrad Gesner, 

 published in 1551-58, and consisting of 4,500 folio pages, with 



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