DEPARTMENT OF MARINE BIOLOGY. 175 



the case. The writer feels, however, that this point should be reinvestigated 

 and, if these results are confirmed, the cause for this difference should be 

 looked after. Perhaps the most remarkable effect of the urea injection is the 

 great increase in the uric-acid content of the blood which results from it. 

 This is especially well shown in experiments where the crawfish had been 

 kept in the live-car for a day or two before the experiment. The uric acid 

 disappears from the blood either completely or practically so. The sample of 

 blood, however, which has been taken 1 to 6 hours after the injection of urea 

 gives a fairly intense uric-acid reaction. This gradually diminishes as the 

 total non-protein nitrogen tends to return to the original level. Although 

 this result may be of considerable theoretical importance, it is nevertheless 

 essential to point out that the uric-acid determinations were made by Bene- 

 dict's new method. This naturally has not been sufficiently tried out yet, 

 though the writer knows of no substance that might, have interfered with the 

 reaction or caused the uric-acid reaction to appear. 



Glucose injected intramuscularly appears very quickly in the blood, and it 

 reaches a much greater concentration than any of the other substances 

 studied. The blood-sugar level, of course, depends more or less directly upon 

 the amount injected, though this is subject to considerable variation. The 

 original blood-sugar level is reestablished in about 12 to 16 hours. The com- 

 parative slowness with which the non-protein nitrogen and the sugar-content 

 of the blood are reduced to original concentration after an injection of urea 

 and glucose as compared to the rapid elimination of ammonium sulphate 

 leads to the belief that these substances are not simply thrown out, but are 

 utilized in the metabolism of the crawfish. The behavior of sucrose as con- 

 trasted with that of glucose presents some interesting points. When a solu- 

 tion of sucrose is injected intramuscularly a rapid rise in the glucose-content 

 of the blood is observed, which, however, is very much less than in the case 

 of glucose injections. On hydrolysis the sugar concentration is found to be 

 considerably greater, thus proving that both sucrose and glucose are present 

 in the blood. The extra glucose must, of course, be derived from the sucrose. 

 This brings up the very important question as to whether the crawfish pos- 

 sesses a sucrase or that such develops when sucrose enters the blood-stream. 

 This problem will form the basis of a future research. It is enough to mention 

 here that already within the first hour after the injection a considerable 

 amount of the sucrose is split up into monosaccharide groups. The writer 

 is unaware that sucrose ever occurs in the normal diet of the crawfish. In 

 one crawfish the curve of distribution of sucrose and glucose (and probably 

 levulose) in the blood was traced for 93 hours. At that advanced time 8 mg. 

 of hydrolyzable sugar were still present, though the blood-sugar level had 

 almost returned to the normal. 



An Analysis of the Blood of a Nurse Shark. 

 The shark was captured and brought immediately to the laboratory, where 

 a sample of blood was obtained directly from the animal's heart. The sample 

 was taken in less than an hour from the time of its capture. The blood 

 was analyzed according to the Folin-Wu system, except that the new Benedict 

 method was used for the uric-acid determination. The deproteinized blood 

 filtrate had the following composition per 100 c. c. blood: 



