1 148 BULLETIN OP THE BUREAU OF FISHERIES. 



extreme diluteness of salt in the above case, I may add that it took the same 

 reading with the specific gravity hydrometer as did tap water. 



In another series of experiments the percentage of hemoglobin was deter- 

 mined with Dare's hemoglobinometer. Although this was less satisfactory, yet 

 the average percentage of hemoglobin of 18 normal Fundulus heteroditiis was 

 found to be considerably more than the average in the case of 29 specimens of the 

 same species kept in fresh water for a certain length of time. Have we, however, a 

 right to say that the corpuscles are thus deficient in hemoglobin ? Since we have 

 good reason for believing that there is an influx of water and that this takes 

 place through the gills, the reduction in number of corpuscles and a lowering of 

 percentage of hemoglobin shows that the blood has been diluted. We can also 

 obtain the specific gravity of the blood. This was done, by the Hammerschlag 

 method, in which a drop of blood is placed in a solution of benzole and chloro- 

 form and enough of each added so that the drop is suspended. The specific 

 gravity of the mixture then would be the same as that of the blood and could 

 be learned by the small hydrometer used for such work. The specific gravity 

 of blood of 20 Fundulus heterocliius was found to be 1.05 10. In an experiment 

 in which 22 Fundulus heteroclitus were kept in fresh water from two to eight 

 hours the average specific gravity of the blood was i .047 -I- . In an experiment 

 in which dogfish {Mustelis canis) were used, the average specific gravity of the 

 blood of three was i .0466. After about two hours immersion in fresh water the 

 average specific gravity was 1.0417. Four determinations were made with each 

 fish in the first part of this experiment and similarly in the second part. There 

 was practically no loss of blood except that used in the determination, which 

 fact is mentioned to anticipate the objection that the reduced specific gravity 

 is due to loss of blood, as in the case of hemorrhage in man, when the specific 

 gravity of the blood drops. 



It is an established fact that the more dilute a solution is as compared with 

 distilled water the nearer is its freezing point to that of distilled water. By the 

 aid of a Beckman thermometer I obtained the freezing point of distilled water 

 and by the same means the freezing point of the blood serum of a number of 

 dogfish. The average lowering of the freezing point of blood serum of 7 dogfish 

 taken from sea water was found to be i .934°. Now if there is a slighter depres- 

 sion in the freezing point of blood serum of dogfish kept in fresh water for a 

 certain period, then that means that the blood of such dogfish has been diluted, 

 for such blood is nearer the condition of distilled water than the normal serum. 

 The depression of the freezing point of the serum of 11 dogfish kept in fresh 

 water for one hour was obtained. The average for five experiments was found 

 to be 1.548°. We have already seen that the depression of the freezing point 

 in case of normal dogfish serum was 1.934°. Hence we find that there was 

 dilution of the blood. 



