292 COLLOIDS IN BIOLOGY AND MEDICINE 



shaped thermocouple. With a muscle of average size, the phenomena 

 are about as follows: Within 3 or 4 minutes there is a very slight 

 cooling; within another 8 or 10 minutes the water freezes in the 

 muscle and further cooling occurs. This part of the curve is quite 

 characteristic for the fixation of water. It should fall more steeply 

 than the curve of control water or of physiological salt solution. If 

 it is less steep, it is "a sign that there is some process in the colloid 

 structures which liberates heat." l In H. W. FISCHER'S and P. JEN- 

 SEN'S investigations, it was shown that it is necessary to distinguish 

 two kinds of water fixation in freezing muscle. "After or during 

 death by freezing, there occurs a phenomenon by which water is fixed 

 in some unknown way and by which it is again liberated at lower tem- 

 peratures," and indeed the amount of water fixed in a muscle in- 

 creases with the amount of disturbance (whether frozen once, twice, 

 heated to 100 or boiled). In this case, also, it is seen that two kinds 

 of water fixation exist. 



The relation between cooling and the death of muscle by freezing 

 is very interesting. The degree of "vitality" was measured by the 

 lifting capacity of a muscle in response to stimulation. It was 

 shown that cooling the muscle to the point of freezing, and even 

 freezing out the water to a certain extent, did no harm, but if the 

 muscle was cooled 1.5 C. more, it died. The inferior thermal margin 

 between life and death of muscle is, therefore, only 1.5 C. wide. 



The normal state of swelling in muscle is conditioned by a normal 

 content of electrolytes. This may vary greatly for different classes 

 of animals; for instance, according to J. KATZ, the striated muscle 

 fibers of the dog contain 3.5 times as much K, and those of the pike 

 14 times as much K, as Na. For the same species it appears to be 

 uniform at the same age. 



A remarkable fact regarding muscles is their high potassium content, 

 which is closely associated with their capacity to functionate. [See 

 MACALLUM, also BURRIDGE. Tr.] For a normal swelling, the iso- 

 tonicity of the surrounding solution appears to be of much less 

 importance than a definite electrolyte content. This follows from 

 experiments of E. M. WIDMARK,* according to which even 10 milli- 

 mols CaCl 2 in the surrounding solution produced a loss of weight 

 amounting to 36 per cent (in the split muscle fibers). 



Muscle Function. 



Every stimulus, whether of thermal, mechanical, electrical or 

 chemical nature causes an irritation in the living muscle which is 

 manifested by a contraction. R. HOBER,* whose investigations we 

 1 The mathematical basis for this is given in the original work. 



