86 



THE AMERICAN MONTHLY 



[March 



result in mammals, shown in blood corpuscles as well as 

 elsewhere. 



Muscle. — The subject of striped muscle has been much 

 worked on, but some of the minor points are the ones of 

 most significance in this present discussion. It is well 

 known that in mammals the nuclei of the fibres lie just 

 under the sarcolemma or limiting membrane of the fibre. 

 In the frog they lie scattered through the sarcous sub- 

 stance. The size and shape of fibre, number, shape and 

 size of nuclei and also the structure of the sarcous sub- 

 stance as apparent from longisections and transections 

 are of significance. The following animals were used: 

 lamprey, amia, frog, amblystoma, cryptobranchus, nectu- 

 rus, snake, turtle, pigeon, and cat. The results are 

 showi> in the following table. 



Warm blooded and cold blooded animals are sharply 

 cut away from each other with one exception the dipnoan 

 Protopterus, in which, strange to say, the nuclei are at 

 the edge as in birds and mammals. On the whole there 

 is about the same number of nuclei, with one exception 

 to be discussed later. The terms coarse and fine are used 

 to describe the appearance of the fibres in transection. 

 This difference in character is probably due to the vary- 

 ing size of the constituent fibrils in different animals. 

 If they are large, a coarse effect results; if small, a fine 

 effect. The same fact explains the diflference in length- 



