14 ZOOLOGY FOR MEDICAL STUDENTS chap. 



chemically simpler materials. And here we see one of the most striking 

 differences between the animal and the vegetable kingdoms. The typical 

 plant by the aid of its green colouring matter or chlorophyll is able 

 during exposure to daylight to take comparatively simple materials such 

 as carbon dioxide and nitrates and build them up into more and more 

 complex substances culminating in living protoplasm. The typical 

 animal is quite unable to do this : it must have its proteins ready provided 

 for it ; and it will be realized from this that the animal world as it exists 

 to-day is dependent for its continued existence upon the vegetable world 

 — for upon the latter depends ultimately the supply of protein food 

 material. 



We have given a description of a particular kind or species of Amoeba — 

 Amoeba proteus — but it will have been gathered from such names as 

 Amoeba Umax and Amoeba radiosa that there are other kinds. It is 

 customary in scientific writing when referring to any particular kind of 

 animal to give it two names — to use what is called the binomial system 

 of nomenclature developed by the great Swedish naturalist Linnaeus 

 (1707-1778). We may conveniently illustrate this system by the case 

 of animals larger and more familiar than Amoeba such as for example 

 the various " cats " large and small which exist as wild animals. Each 

 of the kinds or species — such as the lion, the tiger, the leopard, the jaguar, 

 the puma, the tiger-cat, the lynx, the wild cat — is given a special or 

 specific name, while they are also given a common name, indicating 

 that the several species belong to a group corresponding to the 

 idea conveyed by the English word Cat when used as above in 

 the broad sense. Such a group, of higher order than a species, is 

 termed a genus, and is given a special generic name. In the particular 

 case under discussion the generic name is Felis, while of the various 

 species mentioned the lion is known as Felis leo, the tiger as F. tigris, 

 the leopard as F. pardus, the jaguar as F. oftfa, the puma as F. concolor, 

 the tiger-cat as F. pardalis, the lynx as F. lynx, the wild cat as F. cuius, 

 and so on with other species. It is usual to print such scientific names, 

 which are regarded as Latin substantive and adjective, in italics, and 

 when it is quite clear what is meant the generic name is commonly con- 

 tracted down to its initial letter. The use of such names is not due to 

 mere pedantry : it is rendered necessary for purposes of precision by the 

 fact that popular names are liable to give rise to confusion. Thus such a 

 name as " Crow " is applied in different English-speaking regions of the 

 world to totally different kinds of birds. 



Of the Amoebae a number of species are recognized, differing from 



