418 QUARTERLY CHRONICLE OF MICROSCOPICAL SCtENCE. 



by injection through the aorta the semitendinosus of the 

 rabbit remains distinctly redder than the biceps (see Lankester 

 on "Distribution of Haemoglobin/' ' Proc. Roy. Soc./ 1873). 



Physiologically, these two kinds of muscles differ from 

 each other. When stimulated directly, the red muscles con- 

 tract slowly and progressively, and on cessation of the 

 stimulus again gradually relax. The contraction of the pale 

 muscles, on the other hand, is brusque and sudden. 



If the sciatic nerve be cut in two places, first, at its exit 

 from the sciatic notch ; second, in the middle of the thigh, 

 and the isolated portion stimulated, a contraction of the semi- 

 tendinosus (red) and of the neighbouring pale muscles takes 

 place — the former slowly and gradually, the latter sharply 

 and suddenly. On cessation of the stimulus the pale muscles 

 relax suddenly, while the red muscle returns slowly to its 

 former dimensions. 



As these differences can be observed by direct stimulation 

 in curarised rabbits, it is plain that they are inherent in the 

 muscles themselves, and do not depend on the nervous system. 



There are striking differences of structure in the two 

 groups. The ultimate fibres of the red muscles show very 

 abundant nuclei, disposed in longitudinal rows. In the pale 

 muscles they are scattered and few in number. On trans- 

 verse sections, made after drying and coloured by carmine, 

 four to nine spherical nuclei can be distinguished in each 

 fibre of the red muscles, occupying slight depressions in the 

 muscle substance, or even embedded in its centre. The trans- 

 verse section of a pale muscle-fibre shows no more than one 

 to four flattened nuclei immediately beneath the sarcolemma. 

 In skates and other fishes the muscle substance is separated 

 from the sarcolemma by a granular layer. Flattened nuclei 

 surrounded by a thin layer of protoplasm cover the deep sur- 

 face of the sarcolemma, and others are embedded in the 

 muscle substance. Those which occupy the deep surface of 

 the sarcolemma are much more numerous in the red muscles. 



Ranvier concludes by suggesting that the pale muscles 

 with their sudden contraction may be the muscles of action, 

 while the slowly and more persistently contracting red 

 muscles may have a function of equilibration or regulation. 



3. Living Muscle. — Wagener has made observations on 

 living muscles in the transparent larvae of Corethra plumi- 

 cornis, which he specially recommends for this purpose 

 (' Archiv f. Mikr. Anat.,' x, 293). 



4. Muscles in Typhus. — In another memoir (Ibid, 311), 

 Wagener studies the alterations of muscular tissues in typhus 

 and typhoid fever. 



[Heads VII— XII are unavoidably postponed.] 



