144 



PHYSIOLOGY 



CHAP. 



the 0'90 per cent solution to be isotonic ; and although Winter 

 found the chlorides contained in serum to be, when expressed 

 in terms of NaCl, a little in excess of this figure which re- 

 presents the extreme limit of corpuscular resistance (0-62-0-72 

 per cent) it must be remembered that the osmotic pressure of 

 the blood is due, not only to the chlorides, but, in a minor 

 degree, to other salts and organic molecules, so that the result 

 is considerably higher than it would be for the chlorides alone. 

 On the other hand Winter himself demonstrated, by means of 

 cryoscopy, that on dilution of the serum the molecular concentra- 

 tion is clearly higher than that previously expected from the 

 dilution, which he attributes to dissociation of the molecules of 

 NaCl. Eroiii these observations, that is, from the rich sodium 

 chloride content of blood serum, and from the ready ionisation of 

 its molecules, Winter was led to consider this salt as the com- 

 pensating factor in disorders of the osmotic conditions of the 

 blood and tissue fluids generally. 



These results of Winter, in so far as they concern the relative 

 constancy of the freezing-point of blood serum in mammalia, are 

 unsatisfactory inasmuch as they disagree with the data previously 

 obtained by Hamburger and Gryns, and more recently by 

 Bugarszky and Tangl, and Bottazzi and Ducceschi. Here are 

 some of the data obtained by these authors : 



Gryns. 



Serum of hors 



fowl 



A =0-549 

 0-561 

 0-520 

 0-619 

 0-624 

 0-620 

 0-600 



Bottazzi and Ducceschi. 



Serum of frog 

 toad 



tortoise. 



11 11 



,, cock 

 ,, hare 

 dog 



A =0-563 

 0-761 

 0-463 

 0-485 

 0-623 

 0-564 

 0-576 



Fano and Bottazzi found in a series of cryoscopic observations 

 that the osmotic pressure of dog's serum presents only slight 

 variations from a mean value (higher than that found by Winter), 

 even when the animal has been subjected to the most various 

 organic injuries, such as splenectomy, asphyxia, inanition, anaemia 



