3 02 THE POPULAR SCIENCE MONTHLY. 



ing. He must have a fair knowledge of mechanics, experimental 

 physics, and chemistry ; he ought to (I would almost again say he 

 must) be able, besides English, to read at least French and German 

 with facility assuredly, if he cannot, he will labor with much toil 

 and sorrow and the more mathematics he knows, with the present 

 rapid importation of quantitative ideas into biological science, the 

 better for him ; and for certain special branches of biological work 

 there are other special needs. No mistake is more disastrous than 

 the idea that a man can be a botanist and nothing more ; a zoologist, 

 and nothing more ; a physiologist, and nothing more. It is true that 

 no one can be master of all the physical sciences, but it is none the 

 less true that hardly one of them can be entirely neglected by the 

 biologist. Animals and plants are, after all, material objects, and live 

 in accordance with the laws that govern matter; but the manifesta- 

 tions of these laws are so often obscured and complicated by the con- 

 ditions in which they occur in living things, that the understanding 

 of them is only to be got at by approaching them through their sim- 

 pler manifestations in inorganic bodies. But, apart from that, definite 

 knowledge of various sciences is constantly required by the biologist. 

 How can one ignorant of physics have any real appreciation of the 

 statement that the transmission of a nervous impulse is accompanied 

 by a molecular alteration in the structure of a nerve-fibre, one sign of 

 which is a certain very definite and peculiar alteration in its electrical 

 properties ; or how can one ignorant of chemistry grasp the funda- 

 mental statement that muscular work is in the long-run dependent 

 on the breaking down of complex chemical molecules into simpler 

 and more stable ones? How can the zoologist or botanist scientifically 

 study the distribution of animals and plants in space, unless he has a 

 knowledge of physical geography ; or in time, unless he knows some- 

 thing of geology ? I need not prolong the list. 



Furthermore, no one can properly study any branch of biology 

 without some knowledge of its other divisions. The fundamental 

 laws of animal and vegetable life are identical, and only fully realized 

 by comparison ; so, while the scientific botanist, to fully appreciate the 

 facts of his own science, must be something of a zoologist, so must 

 the zoologist know something of plants : no one living being or group 

 of living beings can be properly understood by itself. To take other 

 examples: how is the morphologist to deal with such problems 

 as those presented to him by rudimentary organs, unless he know 

 something of the functions of parts, which is the special domain of 

 physiology ; or, how is he to understand the influence of external 

 conditions in the production and preservation of variations in force, 

 without, again, this knowledge of function ? And, as regards the physi- 

 ologist, he has frequently to search the whole animal and vegetable 

 kingdoms not only to discover those forms which give him the best 

 opportunity of studying certain phenomena, but also to get at those 



