SCOTT, STUDY OF CHANGES IN MVSTELVS CANIS 43 



corpuscles of four elasmobranchs and six teleosts. Although on the 

 whole, teleost corpuscles are laked by a more dilute solution than is the 

 case with elasmobranch corpuscles, the difference is small as compared 

 with that given by Mosso. The degree of dilution of the solution which 

 first lakes the corpuscles in the two cases is not proportional to the degree 

 of departure from the normal salinity of the blood. Bottazzi and Due- 

 ceschi (^96) pointed out that no parallel relation exists between the re- 

 sistance of the corpuscles and the osmotic pressure of the serum of ani- 

 mals from the different vertebrate phyla. So we may conclude from the 

 above results that whatever be the function of the osmotic pressure of the 

 serum, this is not primarily for the purpose of maintaining the integrity 

 of the corpuscle so far as the retention of its haemoglobin is concerned. 

 We have seen that the haemoglobin is retained even though profound 

 changes in the osmotic pressure of the serum take place. Relatively 

 speaking, elasmobranch corpuscles have a greater range in the resistance 

 of their corpuscles than is the case with regard to marine teleosts. They 

 withstand a greater relative reduction of the osmotic pressure of the sur- 

 rounding medium, i. e., serum, before the hemoglobin is lost, than is the 

 case of the teleosts. That the death of Mustelus is not due to the laking 

 of the blood is seen from the above facts. The swelling of the corpuscles, 

 as shown by haematocrit and centrifuge measurement, is probably a mat- 

 ter of greater importance. The imbibition of water may interfere with 

 the gaseous exchanges in the capillaries of the gills. The blood taken in 

 the centrifuge and haematocrit measurements described here must have 

 been changed in the gill capillaries and continued to circulate. The gill 

 capillaries do not become completely clogged up with broken down cor- 

 puscles as Mosso claimed, as is shown by the fact that the blood used in 

 all these experiments was taken from the caudal artery. The blood of 

 Mustelm is first decidedly laked in a 0.8 per cent NaCl solution. The 

 freezing point of such a solution is — 0.50° ; but it has already been shown 

 that the freezing point of the blood of Mustelus at the time of death in 

 fresh water is about — 1.45°, which indicates a dilution insufficient to 

 cause laking. It may be, however, that the stream of blood flowing 

 through the capillaries of the gills is met by an influx of water sufficient 

 to lake some of the corpuscles as they pass by. The experiments demon- 

 strate individual differences in corpuscles, since some are laked and some 

 are not. Whether or not all of the corpuscles are swollen would be diffi- 

 cult or even impossible to determine. The fact that some corpuscles are 

 laked, while the great majority retain their integrity, warrants the con- 

 clusion that not all the corpuscles are swollen. 



