A CROSS-STKIATED MAMMALIAN MUSCLE PKEPARATIOX. By 

 R. J. S. M'DowALL.^ (From the Department of Physiology, 

 Edinbiirf,'h T"^niversity.) (Witli nine figures in the text.) 



Ordinary mammalian muscle is disadvantageous for experimental work, 

 since it dies soon after removal from the body unless kept at about body 

 temperature and perfused with oxygenated blood or other suitable fluid. 



Although the retractor penis of the hedgehog, which consists of plain 

 muscle, is known to live for a long time after removal from the body and 

 without perfusion, it does not seem to be generally known that certain 

 cross-striated muscles of the same animal retain their functions equally 

 well under these circumstances, and are otherwise not unsuitable for 

 experimentation under ordinary laboratoiy conditions. 



The muscles in cjuestion are those concerned with the rolling of the 

 animal into a ball and the subsequent unrolling. These muscles and their 

 actions are described by Huxley in his Anatomy of the Vertebrata. 

 They are composed, as already stated, of cross-striated fibres, although it 

 must be stated that in some of them appearances are seen which suggest 

 incomplete histogenesis. 



They fall into two groups, according to their form and attachments. 

 One, the orbicularis dorsalis, a very thick circular band of fibres, plays 

 the chief part in the curling up of the animal. It is, however, so closely 

 incorporated with the skin that it cannot readily be dissected oflT without 

 lacerating its fibres. The other group, which is concerned in starting both 

 the rolling and the unrolling process, is formed of straight, parallel- 

 fibred muscles which arise from the trunk and are inserted into the skin. 

 There is no diflSculty in dissecting them out in their whole length (5-7 cm.) 

 without damage. Removed from the body and kept at ordinary laboratory 

 temperature, without perfusion or special oxygenation, they continue excit- 

 able for at least twenty-four hours. They contract on stimulation at all 

 temperatures, from 0° to 40° C. 



In the experiments shown in the illustrations accompanying this paper 

 the Keith-Lucas method of stimulation was employed. By this method 

 the w^hole diameter of a muscle is made to complete a circuit between two 

 electrolytic solutions : thus all the fibres of the muscle are stimulated and 



1 The observations embodied in this paper were made four years ago. It was intended 

 to pursue the investigation further in the following year, but the war prevented this inten- 

 tion being carried out ; and as the author is still on military service, it has been thought 

 well not to delay publication any longer. — [Ed.] 



