SCOTT, STUDY OF CHANGES IX MUSTELUS CAN IS 5 



Director of the New York Aquarium. I must also express my indebted- 

 ness to Professors Frederic S. Lee and F. H. Pike of the Department of 

 Physiology of Columbia University for many helpful suggestions. 



Historical 



Sumner (^06) published a brief summary of investigations of the os- 

 motic relations of the body fluids of aquatic animals to their surrounding 

 medium. Bottazzi ('07 ) has given an extensive review of the literature 

 bearing on this subject. I will limit this synopsis, therefore, to a brief 

 statement of investigations on the osmotic relations of the elasmobranchs 

 to the surrounding medium. Constant reference will be made to investi- 

 gations on other forms in the pages that follow. 



Mosso (^90) observed that elasmobranchs died very soon after being 

 placed in fresh water. He explained the death as being due to the fact 

 that the erythrocytes were laked by the influx of fresh water into the 

 capillaries of the gill membranes, that the capillaries were clogged up 

 with these broken down corpuscles, that circulation was thus stopped and 

 that death ensued from asphyxiation. Von Schroeder ('90) found a large 

 amount of urea, 2.6 per cent, in the blood and other tissues of the normal 

 dog-fish. Quinton ('90 ) confirmed this statement of von Schroeder's. 

 Rodier ('00) found at Arcachon on the southwest coast of France that 

 the A's of the blood serum of different species of elasmobranchs were 

 similar, although slightly lower than that of the sea-water in which they 

 lived. The pericardial, peritoneal and uterine liquids had the same A as 

 the blood serum. He also corroborated the discovery of von Schroeder as 

 to the presence of urea in the blood of elasmobranchs and called atten- 

 tion to its role in determining the osmotic pressure of the blood. He 

 found that the bile and urine contained less chlorine than the blood. 

 Fredericq ('04) confirmed Eodier's statement witli regard to the role of 

 urea in maintaining the osmotic pressure of the blood. He found that if 

 one puts a dog-fish, Scyllium, into concentrated or diluted sea-water, 

 equilibrium between the osmotic pressure of the internal medium and the 

 external medium takes place in a short time, due to the withdrawal or 

 addition of water from the blood without involving the dissolved sub- 

 stances of the blood. Garrey ('05) found that the blood of the elasmo- 

 branchs from Woods Hole is isotonic with the sea-water and that dilution 

 or concentration of sea-water causes a similar change in the blood of 

 selachians immersed in such modified media, but that death ensues before 

 an equilibrium is established. He concluded that the limiting mem- 

 branes of the selachian body are semi-permeable. Bottazzi ('06) showed 

 that not only the blood but also the urine, uterine fluid and the bile of 



