GENERAL CONSIDERATIONS ON TSE STRIPED MUSCLES. 181 



By desiccation, muscles become hard and brown ; by repeated washing 

 they assume a straw-yellow tint. 



Muscles are extensible and elastic ; they are also tenacious, and their 

 tenacity is more marked during life than after death. 



It has been remarked that the juice impregnating the muscular tissue is 

 distinguished from the serum of the blood by an acid reaction. (The fluid or 

 " muscle plasma " obtained by pressing flesh, is either neutral or slightly 

 alkaline. It soon coagulates and separates into two portions — a semi-solid 

 portion, " myosin," and the fluid serum that at ordinary temperatures quickly 

 acquires an acid reaction.) It holds in solution a variable quantity of 

 albumen, casein, fat, a little creatine, creatinine, and a somewhat large 

 proportion of lactic acid. The solid substance of the muscle may be partly 

 transformed into gelatine by boiling in water ; but its largest portion is a 

 nitrogenous substance, soluble in dilute hydrochloric acid, called " syntonine," 

 or muscular fibrine : it difiers but little from the flbrine of the blood. 



PHYSIOLOGICAL PEOPBBTIES OF THE STRIPED MUSCLES. 



In this paragraph will only be discussed the development of the muscles, 

 muscular contractility, and the part the muscles assume in locomotioii. 



A. Development op the Muscles.— A muscle is derived from a mass of 

 embryonic cells. Each cell becomes considerably elongated, and its nucleus 

 becomes multiple, to constitute a muscular fibre. The membrane of the cell, 

 enormously developed, forms the sarcolemma, while the contents of the cell, 

 becoming more dense, divide longitudinally and give rise to the contractile 

 fibrillsB. Lastly, when the muscles are formed, they grow by the augmenta- 

 tion in length and thickness of the primary fasciculi or muscular fibres. 



'B. Muscular Contractibilitt. — Muscles possess the property of con- 

 tracting under the influence of a natural or artificial stimulus. Muscular 

 contraction is the phenomenon resulting from the operation of this property. 

 Muscles in a state of contraction are the seat of physical and chemical 

 phenomena ; they change their form and consistency ,.and become the theatre 

 of a relatively abundant production of carbonic acid, creatinine, and inosinic 

 acid. During contraction, it has been remarked that the muscular fibres 

 contract by increasing in volume, like an india-rubber tube left to itself after 

 being extended : the zig-zag doubling mentioned by Prevost and Dimias has 

 not been observed. 



But these physical and chemical modifications, important as they are in 



Fig. 100. 



MUSCULAR FIBRE KT A STATE OF CONTRACTION IN THE CENTRE; THE STEI^ 

 approximated; the breadth of the fibre INCREASED; AND THE MYO- 

 LEMMA RAISED IN VESICLES ON ITS SURFACE. 



a physiological point of view, cannot longer be dwelt upon here. It is parti- 

 cularly important to speak of muscular contraction. 



A muscle that contracts becomes shortened ; its two extremities approach 

 each other if they are free ; or one draWs near the other if the latter is fixed 

 15 



