SCOTT, STUDY OF CHANGES IN illSTELVS CANIS 



33 



Table XIII. — Change in A of hlood of Squalus acanthlas after immersion in 



fresh ivater for one hour 



No. 



Length in 

 cm. 



Rise in A alter .30 



minutes in fresh 



water 



Rise in a after 



(JO minutes in 



fresh water 



1 



2 

 3 

 4 



56 

 58 

 61 

 61 



+0.090° 

 +0.085 

 +0.130 

 +0.090 



+0.110° 

 +0.160 

 +0.260 

 +0.130 



f 0.40 



t0.20 



The average change during the first half hour is +0.099° and at the 

 end of an hour amounts to +0.165°. At the end of the same period in 

 fresh water the blood of Mustelus had changed about 0.30°. At first it 

 might be thought that the smaller change in the spiny dog-fish indicates 

 an acquired immunity to the effects of dilute solutions of sea-water. It is 

 possible that the limiting membranes of the body have become less per- 

 meable, thus preventing such a great change as in the blood of Mustelus^ 

 in the experiments with which the change in the external medium was 

 greater. But, as was claimed above, the A of the blood of Squalus has 

 risen 0.18°, due to the difference be- 

 tween the molecular concentration of 

 sea-water and harbor water. Moreover 

 the freezing point of its blood has risen 

 an additional 0.16°, due to the trans- 

 ference of the fish from harbor water 

 to fresh water. The total change is 

 thus 0.34°, or nearly as great as that 

 taking place in the blood of Mustelus, 

 which was transferred directly from 

 sea-water to fresh water. If this 

 equality of modification in the osmotic 

 pressure of the blood be true, then it follows that the limiting mem- 

 branes of Squalus have acquired little or no resistance to the external 

 medium; for their permeability has not changed. The change in the 

 osmotic pressure of the blood is still proportional to the change in the 

 osmotic pressure of the external medium. In Fig. 3, the point E, on line 

 C — D, represents the A of the blood of Squalus from harbor water, which 

 has a A of about 1.00°. Fig. 6 shows the changes in A of blood of 

 Squalus due to immersion in fresh water. It will be noted that the in- 

 itial A of the blood is .18° above the normal A of the blood in sea-water, 

 and that although at the end of an hour in fresh water it has risen but 

 0.16°, yet it is 0.34° higher than the normal A in sea-water. 



20' 40" 6or 



Fig. 6. — Changes in the \ of hlood of 

 Squalus due to tran-^ference from 

 harbor xcater to fresh water. A, 

 in harbor water; B, 30 minutes in 

 fresh; C, 60 minutes in fresh. 



