ON BIOLOGY. 23 



very general comprehension of the laws and factors of 

 this doctrine considered in its entirety. When we come 

 to search for the physical basis in the economy of any 

 living thing in the whole world, it invariably results in 

 the discovery of an apparently structureless mass, to 

 which the name of protoplasm has been given. This 

 fundamental form of all life; this morphological unit is 

 the material, in so far as our present knowledge carries 

 us, from which every organ, however complex or how- 

 ever high in the scale of organization in either the animal 

 or vegetable kingdom, is built up. Among some of the 

 lowest forms of existing life we find that, structurally, 

 they are but slightly advanced beyond this protoplasmic 

 matter; whereas in man or any other complex animal, 

 his system is found to be made up of 

 organs and tissues, which organs and tis- 

 sues are in turn found to be simply an aggregation of 

 protoplasmic cells, that present various modifications in 

 form, which latter takes on an internal structureless 

 part and an external part which appears to be more defi- 

 nitely constituted. Further, it is apparent that this liv- 

 ing matter, considered in its simple state, holds a definite 

 position in space and in time; it may be acted upon by 

 certain forces, which result in the production in it of cer- 

 tain internal changes or causes it to modify external ob- 

 jects, which in turn may modify it. So that, finally, its 

 very form, or the place it occupies, or what it is capable 

 of doing are controlled by the effects of certain causes. 



Our ablest biologists then subdivide the entire subject 

 of biology into four parts, that is, into morphology, dis- 

 tribution, physiology and aetiology. 



As I have already pointed out, under morphology we 

 take into consideration both the minute and gross anat- 

 omy of all living forms, together with their development. 

 Such knowledge is made comparative, and taxonomy or 

 classification flows from it as a natural result. 



Under distribution we arrange all the facts that bear 

 upon the occurrence of living forms over the surface of 

 the globe, and the laws that appear to govern it, as well 

 as the geographical occurrence of animals and plants 

 during former geological epochs of the earth's history. 

 Under physiology we have to deal with the functions 

 of living matter as seen in the representatives of the animal 

 and vegetable worlds, of the function of an organ of any 

 living thing as a whole, and the functions of the mor- 

 phological units or cells of which any living thing is 

 composed. Secondly, of the various modes of reproduo- 



