612 
G. H. DREW. 
with a diamond, broken clean across, and passed through the 
flame, so as to obviate jagged ends, which tend to cause an 
agglutination of the corpuscles around the end of the tube. 
Description op the Blood. 
The blood of Cardium norvegicum is a somewhat 
opalescent fluid, appearing slightly yellow by transmitted, 
and blue by reflected, light. On shaking, the corpuscles 
stick together, forming small white floccular masses which 
fall to the bottom of the liquid. 
The plasma can be obtained free from the corpuscles by 
filtering, and appears of tlie same colour as the blood. It 
contains hmmocyaniu (Cuenot) (2). Its reaction to litmus is 
neutral. On heating to 74° C. it becomes distinctly cloudy, 
and in time a floccular precipitate of coagulated proteid is 
produced, which is soluble in alkalies and acids, but is re- 
precipitated on neutralisation. The addition of an equal 
volume of 90 per cent, alcohol produces a white precipitate. 
The plasma gives the usual proteid reactions, such as the 
xanthoproteic and Biuret reactions, a brick-red precipitate 
with Millon’s reagent, a white ring on the addition of nitric 
acid (which does not disappear on warming), and a white 
precipitate with potassium ferrocyanide and acetic acid. 
An analysis of the blood for salinity, by titration with 
silver nitrate, using potassium chromate as an indicator, gave 
a chlorine value very slightly higher than that of the sea- 
water in which the animal was living’. This small increase 
was probably due to evaporation while collecting the blood, 
boiling to remove the hmuiocyanin, and filtering. Without 
very specialised apparatus it is almost impossible to go 
through these operations without a small loss due to evapora- 
tion. 
Cuenot has estimated the total salts in the blood of a 
number of marine invertebrates living in waters of various 
salinities. He evapoi-ates and incinerates the blood, and 
estimates the salts gravimetrically. By this method he 
