CHEMICAL COMPOSITION OF THE MUSCLES 421 



nective tissue. The cells are known as connective-tissue cells. They 

 are irregular in size and form, some being spindle-shaped or caudate, 

 and others, star-shaped. They possess one, and sometimes two or three, 

 clear ovoid nuclei with distinct nucleoli. On the addition of acetic acid 

 the cells disappear, but the nuclei are unaffected. It is impossible to 

 give accurate measurements of the cells on account of their great varia- 

 tions in size. Between the muscles, and in the substance of the muscles 

 between the bundles of fibres, there always exists a greater or less quan- 

 tity of adipose tissue in the meshes of the fibrous structure. 



Bloodvessels and Lymphatics. The muscles are abundantly supplied 

 with bloodvessels, usually by a number of small arteries with two satel- 

 lite veins. The capillary arrangement in this tissue is peculiar. From 

 the smallest arterioles, capillary vessels are given off, arranged in a net- 

 work with tolerably regular, oblong, rectangular meshes, their long 

 diameter following the direction of the fibres. These envelop each 

 primitive fasciculus, enclosing it completely, the artery and vein being 

 on the same side. The capillaries are smaller than in any other part of 

 the vascular system (see Plate X, Fig. i). 



The arrangement of the lymphatics in the muscles has not been 

 definitely ascertained. There are lymphatics surrounding the large 

 vascular trunks of the extremities and of the abdominal and thoracic 

 walls, which, it would appear, must come from the substance of the 

 muscles ; but they have not been traced to their origin. 



Connection of the Mtiscles with the Tendons. The primitive mus- 

 cular fasciculi terminate in little conical extremities that are received 

 into corresponding depressions in the bundles of fibres composing the 

 tendons ; but this union is so close that the muscle or the tendon may 

 be ruptured without a separation at the point of union. In the penni- 

 form muscles this arrangement is quite uniform. In other muscles 

 it is essentially the same, but the perimysium seems to be continuous 

 with the loose fibrous tissue enveloping the corresponding tendinous 

 bundles. 



Chemical Composition of the Muscles. The most important proteid 

 constituent of the muscles is myosin. This resembles fibrin, but it 

 presents certain points of difference in its behavior to reagents, by which 

 it may be readily distinguished. One of its peculiar properties is that 

 it is dissolved at an ordinary temperature by a mixture of one part of 

 hydrochloric acid and ten of water. Myosin is now regarded as a com- 

 pound substance containing at least four different proteids that may 

 be separated by fractional heat-coagulation : (i) A globulin that coagu- 

 lates at about 117 Fahr. (47 C.). This is called paramyosinogen. (2) A 

 globulin that coagulates at 133 Fahr. (56 C.). (3) A globulin that 



