SCOTT, STUDY OF CHANGES IN MUSTELUS CANIS 39 



was as 20.5 to 79.5. After immersion in fresh water the ratio was 30.77 

 to 69.23. Fig. 8 shows this difference. In this figure, N represents the 

 ratio between the volume of corpuscles and serum in normal blood. H 

 represents the ratio from blood taken from fishes after immersion in 

 fresh water. Shaded portions represent corpuscles. Considering these 

 results in connection with those obtained by the use of the camera lucida, 

 we may conclude that at least some of the corpuscles are swollen after 

 immersion of the fish in fresh water. The faint trace of laking at the 

 end of the experiment indicates that at least some of these swollen cor- 

 puscles cannot withstand the increased pressure of distension by the ab- 

 sorption of water. These burst and cause the faint trace of laking noted 

 above. In fact, in preparations made of the corpuscles of a fish that had 

 died in fresh water, some corpuscles were found broken down. 



Since Mosso claimed that the resistance of the erythrocytes of fishes 

 varied in a general way with the salt content of the blood, I determined 

 to ascertain the strength of solutions of NaCl which would cause the- 

 laking of the blood of elasmobranchs common at Woods Hole. He found 

 that the erythrocytes of selachians at Naples were laked by solutions more 

 dilute than 2.5 per cent NaCl. The sea-water from the Mediterranean is 

 isotonic with a 3.8 per cent sodium chloride solution. A 2.5 per cent 

 sodium chloride solution is about 34 per cent more dilute than the water 

 from the Mediterranean. A reduction of 34 per cent in the salinity of 

 the sea- water from Woods Hole would give a solution isotonic with 1.2 

 per cent solution of NaCl. So that according to Mosso's hypothesis the 

 blood of the Woods Hole elasmobranchs should be laked in a 1.2 per cent 

 solution of NaCl and in all solutions more dilute than this. I made up 

 ten solutions of NaCl. The first was a 2 per cent solution, the second a 

 1.8 per cent solution, the remaining solutions decreased respectively 0.2 

 per cent, the last being a .2 per cent solution. I tried the effect of these 

 solutions on the defibrinated blood of the smooth dog-fish, Mustelus canis, 

 the spiny dog-fish, Squalus acanthias, the sand shark, Carcharias litto- 

 ralis, and the skate, Eaia erniacea. Following are the results of the ex- 

 periments : 



Experiment 1. Squalus acanthias. Male. 29 inches long. 



No laking in 2 per cent NaCl to 1.0 per cent NaCl. Faint trace in 0.8 per 

 cent NaCl. Decided in 0.6 per cent NaCl. 



Male. 194- inches long. 



Same results as above. 

 Experiment 2. Mustelus canis. Male. 20 inches long. 



No laking in 2 per cent NaCl to 1.2 per cent NaCl. Faintest trace in 1 

 per cent NaCl. Decided in 0.8 per cent NaCl. 



Male. 29 inches long. 



Results same as above. 



