BIOLOGICAL METHODS I7 



phenomena which contribute to the edification of the hving 

 being as a whole is therefore quite natural. No matter how 

 much a motor is tampered with, one cannot hope to know how 

 it works without taking it to pieces. This brings us to the second 

 class of methods, which can be called the 'breaking-down 

 methods' and on which we will say a few words. 



These methods are static or dynamic. To study an 

 organism statically it is necessary to begin by kilHng it. All 

 descriptive sciences, such as anatomy, cytology, histology, 

 embryology, compel the worker, at a given moment, to act 

 like a curious child who breaks his toy so as to see the 

 mechanism. Thanks to anatomy, we have acquired a perfect 

 knowledge of the location and the shape of our organs, our 

 muscles and the levers which they command, the bones. 

 Anatomy, enlarging the field of its activity under the name of 

 comparative anatomy, established enlightening analogies 

 between living beings from the bottom to the top of the ladder. 

 And not only between those living to-day, but between these 

 and those which became extinct long ago. Anatomy is at the 

 base of our knowledge of evolution in organized beings. It 

 has rendered possible the notion of filiation of species and the 

 issuance of a good many hypotheses which probably all contain 

 a part of the truth, without one of them, it must be admitted, 

 being able by itself to account for natural evolution. 



The famous theories of Lamarck, Darwin, and de Vries 

 have been the object of numerous critical works which are of 

 great interest, and the reader is referred to the many books 

 which exist on the subject. 



Cytology, the science of cells, depends wholly on the use of 

 the microscope as a tool of investigation, coupled together 

 with selective dyes. The tissues are usually embedded in a 

 block of paraffin wax which, when cool, maintains the fragile 

 cellular elements so that they can be sliced in extremely thin 

 layers, a thousandth of an inch thick. The entire sample of 

 tissue having thus been cut into a considerable number of 

 transparent pieces, it can readily be understood that the 

 examination of a successive series enables the scientist to 



