Transactions of The Royal Society of Canada 



SECTION IV 

 Series III DECEMBER 1917 AND MARCH 1918 Vol. XI 



The Histogenesis of Vertebrate Striated Muscle, including a Contribution 



to our Knowledge regardi?tg the Structure and Functions of 



the Cell- Nucleus. 



By John Cameron, M.D., D.Sc, F.R.S.E. 



Presented by Dr. C. Gordon Hewitt, F.R.S.C. 

 (Read May Meeting, 1917.) 



I. Introductory. 



The results of the present research are founded upon the examina- 

 tion of embryos ♦representing the five great vertebrate classes. After 

 making an examination of several species, it was decided to select 

 embryos of Zoarces vivipara to represent the class of fishes, owing to 

 the large size and clear differentiation of the sarcous elements in this 

 animal (see Figs. 1, 11 and 12). I would without hesitation recom- 

 mend this species to all investigators who wish to study the subject. 

 Rana temporaria was found convenient and satisfactory in every way 

 as a representative Amphibian type. Lacerta was chosen to represent 

 reptilia, while rat and chick embryos were utilised for the purposes 

 of the investigation in mammals and birds. As, however, the various 

 sarcous elements were found to be proportionately large in the lower 

 vertebrate types, the conclusions arrived at in this memoir are largely 

 founded upon a study of these. The individual sarcous elements 

 in mammals are relatively minute, so that micro-photographs pre- 

 pared from that vertebrate class were found unsuitable for reproduc- 

 tion. It may be stated, however, that the mode of myogenesis was 

 found to be essentially the same in all vertebrate classes 



II, Fixation of the Embryos. 



The next question to settle was the choice of a fixative. I was 

 here faced by a grave difficulty, since fixing agents act as a stimulus 

 to living muscle, and cause it immediately to contract. However, 

 after numerous experiments, the substance known by the name of 



Sec. IV. Sig. 6 



