m ANNALS NEW YORK ACADEMY OF SCIENCES 



counted for. Macallum ('10) found that the urea and salts of the serum 

 of Acanthias vulgaris would not account for its freezing point. He con- 

 cluded that the difference between the freezing point of serum and that 

 produced by the combined salts and urea was due to the other organic 

 solutes. These were found to be ammonia salts, which were present in 

 amounts sufficient to account for the additional depression of the freez- 

 ing point. We may infer that ammonia salts are present in the blood of 

 Mustelus. By these and other organic solutes, such as sugar, the freez- 

 ing point of the blood is brought to — 1.87°. The role of these sub- 

 stances, which are also crystalloids, has been too much neglected. 



Mines ('12) described the effects of electrolytes on the elasmobranch 

 heart. The work was done at the laboratory of the Marine Biological 

 Laboratory at Plymouth, England. The normal freezing point of the 

 forms used was probably similar to that of Mustelus, namely, — 1.87°. 

 Records were made showing the effects of solutions perfusing the heart. 

 The fluid was adapted from one used successfully by Knowlton, whose 

 results have not as yet been published. From the formula giyen by him, 

 I conclude that Mines's solution must have had a freezing point less than 

 — 1.52°. In other words, the solution was hypotonic to the blood which 

 normally bathed the heart. It contained about the same percentage com- 

 position of metallic elements (sodium, potassium, calcium and magne- 

 sium) as determined by Macallum, and urea and chlorides as determined 

 by myself. Since each of the kations has been shown by Mines to have a 

 specific effect on the heart action, his perfusion solution probably con- 

 tained the optimum amount of these substances. Baglioni's experiments 

 on the maintenance of the heart beat of elasmobranchs were carried on 

 at Naples, where the mean freezing point of elasmobranch blood is 

 — 2.29°. The author used two solutions, one being a 3.5 per cent solu- 

 tion of sodium chloride, which is isotonic with the blood. The other 

 solution consisted of 2 per cent sodium chloride -|- 2.2 per cent urea plus 

 a trace of calcium chloride. The computed freezing point of such a solu- 

 tion is about — 2.00°. The freezing point of a solution of 2 per cent 

 urea -f- 2 per cent NaCl obtained by means of the Beckmann apparatus 

 is about 1.80°. Hence the solution with which Baglioni obtained his 

 results was in all probability somewhat hypotonic to the blood of the elas- 

 mobranchs he used. 



If we subtract from the normal freezing point of the blood, the freez- 

 ing point due to the salts, i. e., about — 0.85°, there is a remainder of 

 — 1.02° which is caused by urea and other substances in solution. It has 

 been noted that when the fish is immersed in fresh water, the nitrogenous 

 substances are decreased at death by 15.5 per cent. The freezing point 



