1882.] Organic Physics. 557 



develop, it might yield myriads of mature offspring. For such an 

 important and continued function, provision must be made, and 

 this provision must exist in some duty naturally arising from the 

 chemical and organized constitution of 'the body. 



Efforts have been made to explain this phenomenon, of which 

 the most notable are those of Spencer and Darwin. Spencer 

 advances a hypothesis of physiological units, in some way inter- 

 mediate between the molecular and the cellular units of the body, 

 and being in themselves generalized copies of the body. He 

 does not think it possible that this generalism can exist in the 

 molecules themselves. 



The hypothesis advanced by Darwin is more satisfactory, 

 though equally without visible support. He proposes the idea 

 that every portion of the body is constantly throwing off invisi- 



body itself, some brought into it from ancestral bodies. These 

 gemmules, he thinks, contain the special characteristics of the 

 part from which they arise, pass into the blood current, multiply 

 by self division, and finally aggregate into a reproductive germ, 

 whose development may reproduce the parent organism and, to 

 some extent, that of more remote ancestors. 



This pangenesis hypothesis approaches a physical explanation 

 of the difficulty, although it seems in certain respects insufficient 

 In fact, no such hypothesis may be needed. If the body is en- 

 gaged in so incessant a labor we might reasonably expect to dis- 

 cover some visible evidence of such an important function. And 

 certainly a very cursory examination of the body yields us evi- 

 dence which seems to offer a satisfactory solution of this difficult 

 problem. It may seem strange if we assert that every portion of 

 every tissue is constantly giving off, or in some way influencing 

 the formation of organized substance; that this substance is not 

 invisible, like the pangenetic gemmules, but perfectly visible; that 

 it has no discoverable office in the body, and that its organization 

 is that of a fully vitalized germ. 



Vet such a material does exist, and is that known as the leu- 

 cocyte, or the white blood corpuscle. The office of this corpuscle 

 has been, and still is, a puzzle to physiologists. They suppose 

 that it may be converted into the red blood corpuscle, yet this 

 remains a supposition only. If we closely examine the origin 

 and character of the leucocytes we may feel warranted in ascrib- 



