THE MUSCULAK SYSTEM. 403 



precipitated by saturation with sodium chloride, or magnesium sulphate, 

 and which can he coagulated at 63 C. (b.) Serum-albumin, which 

 coagulates at 73 0., but is not precipitated by saturation with either of 

 those salts. And (c.) Myo-albumin, which is neither precipitated by 

 heat, nor by saturation with sodium chloride or magnesium sulphate, 

 but may be by saturation with ammonium sulphate. It is closely con- 

 nected with, even if it is not itself, myosin ferment. Neither casein nor 

 peptone has been found by Halliburton in muscle extracts. In extracts 

 of muscles, especially of red muscles, there is a certain amount of Hce- 

 moglobin, and also of a pigment special to muscle, called by McMunn 

 Myo-hcematin, which has a spectrum quite distinct from hsemoglobin, 

 viz., a narrow band just before D, two very narrow between D and E, 

 and two other faint bands, near the violet, E b, and between E and F 

 close to F (McMunn). 



B. Ferments. In addition to muscle ferments, already mentioned, 

 muscle extracts contain certain small amounts of pepsin and fibrin fer- 

 ment, and also of an amyloly tic ferment. 



C. Acids, particularly sarco-lactic, also acetic and formic. 



D. Glycogen and Glucose, also Inosite. 



E. Nitrogenous crystalline bodies, such as Kreatin, Hypoxanthin, 

 or carnin, Taurin and Urea, the last in very small amount. 



F. Salts, the chief of which is potassium phosphate. 



III. PHYSIOLOGY OF MUSCLE. 



Muscle may exist in three different conditions: A. during rest; B. 

 during activity; and C. in rigor. 



A. Rest 



* ^X- 



Physical condition. During rest or inactivity a muscle has a slight 

 but very perfect Elasticity; it admits of being considerably stretched ; 

 but returns readily and completely to its normal condition. In the liv- 

 ing body the muscles are always stretched somewhat beyond their natural 

 length; they are always in a condition of slight tension; an arrangement 

 which enables the whole force of the contraction to be utilized in ap- 

 proximating the points of attachment. It is obvious that if the muscles 

 were lax, the first part of the contraction until the muscle became tight 

 would be wasted. 



There is no doubt that even in a condition of rest Oxygen is abstract- 

 ed from the blood, and carbonic acid is given out by a muscle; for the 

 blood becomes venous in the transit, and since the muscles form by far 

 the largest element in the composition of the body, chemical changes 

 must be constantly going on in them as in other tissues and organs, al- 

 though not necessarily accompanied by contraction. When cut out of 



