EFFECT OF TEMPERATURE ON ANIMAL TISSUES. 5 I 



curves are entirely typical of the results obtained in both cases. 



In considering the temperature effects we may classify them as 

 regards their bearing on the absorption phenomena in the three 

 classes of solutions mentioned above. 



First, of those salts whose solutions, isotonic with m/S NaCl, 

 cause an absorption of water at the normal temperature (20 C), 

 the following were used : NaCl, KC1, NH 4 C1, Na 2 SO 4 , K 2 SO 4 

 and K 2 C O 4 . In all of them, as is shown by the curves, the ab- 

 sorption of water varies directly with the temperature up to a 

 certain critical point, in the neighborhood of 25C., at which a 

 sudden loss of water commences which increases rapidly with a 

 further elevation of temperature. The form of the curve is the 

 same for all the solutions, regardless of whether the initial ab- 

 sorption is great or small, and at about 5oC. the loss of water 

 becomes practically the same in all the solutions. The form of 

 these curves is strikingly like that showing the direct effect of 

 temperature upon the amount of water in protoplasm, indepen- 

 dently of the specific action of any salt solution, as is shown by 

 the curve for ;/8 NaCl which approximates as nearly as possible 

 the fluid which normally bathes the muscle during life, as far as 

 its chemical composition is concerned. For these reasons it 

 seems probable that the effect of temperature upon the absorp- 

 tion of water in these solutions is due to the physical changes 

 induced by the variations in the temperature in the protoplasm 

 of the muscle. The rise in temperature may also accelerate the 

 specific chemical action of the solution upon the muscle proteids, 

 but in any event this only increases the result produced by the 

 temperature alone. The amount of water in the protoplasm of a 

 Protozoan varies directly with the temperature up to the critical 

 point which marks the beginning of heat rigor, and it is interest- 

 ing to find that the same thing occurs in muscle when immersed 

 in solutions which are isotonic with its own substance. Above 

 the critical point the heat rigor causes the same loss of water in 

 all the solutions regardless of their chemical composition. 



The same temperature effects are still better shown in curves 

 of the absorption in solutions of the second class, /. t\, those 

 which cause neither a gain or loss of water in the muscle at the 

 normal temperature. Of the solutions of these salts, three were 



