Evidencr from Somatic Histogenesis 63 



factors, we are now especially attracted by the functional 

 aspect of the subject. To an unsophisticated physiologist 

 studying the phenomena involved in this question, it would 

 probably never occur that more than one answer is possible. 

 Well-informed as such a physiologist may be supposed to be 

 on the important part known to be played by the nucleus in 

 the life of the cell, he would undoubtedly take it for granted 

 that the whole nucleus, its chromatin with the rest, con- 

 tributes in some fundamental way to the result. But unless 

 well indoctrinated beforehand with the chromosome dogma 

 of heredity, he would almost certainly be amazed were 

 some one to contend seriously that the cytoplasm is not the 

 material basis of the hereditary peculiarities exhibited. He 

 would reply, "Why, you are virtually denying that the 

 substance of the muscle fiber is the real seat of muscular 

 activity, thus implying a contradiction of the 'universally 

 accepted principle that the potential chemical energy of the 

 muscle substance is the primary source of muscular energy 

 in all its manifestations' 2e for surely muscular energy 'in 

 all its manifestations' would'include those elements of mus- 

 cular activity which are hereditarily distinctive of different 

 kinds of animals." 



That the cytoplasm is at least the main source of the 

 muscle substance furnishing this energy would not be ques- 

 tioned, probably, by any histologist, but the definiteness of 

 view held at the present time on this subject is worth re- 

 calling and is indicated by such statements as the following: 

 "The energy of contraction is the transformed surface- 

 energy of the ultimate structural elements or colloidal par- 

 ticles (submicrons) composing the fibrils." 27 



Presumably there would be much difference of view among 

 physiologists as to the validity of the chemico-physical part 

 of Lillie's theory of muscular contraction ; but apparently 

 there would be very little dissent from that part of his view 

 which locates the processes, whatever their exact nature, in 



