1910:] Blood in Vertebrates and Invertebrates. 



609 



slightly acidified with acetic acid and heated, in order to coagulate the 

 proteids, which were then removed by filtration. To the filtrate, which was 

 clear, or had only a faint opalescence, some hydrochloric acid and a solution 

 of barium chloride were added, and, after the fluid was heated almost to 

 boiling, it was allowed to stand for 24 hourS; w'lieu the precipitate of barium 

 sulphate was removed by filtration and its weight determined. 



The determination of that part of the depression of the freezing point (A) 

 of a specimen of plasma or serum, due to the salts in it, was carried out in 

 the following way : The weighed quantity of the blood (lobster and horseshoe 

 crab) or serum (cod, pollock, and dog-fish) was evaporated to dryness, first on 

 the water-bath, then in an oven at 115° C. for six hours. The residue was 

 now carbonised at a low heat, and the carbonised residue then extracted 

 several times with hot water containing hydrochloric acid, the remaining 

 material completely incinerated at dull red heat, the ash dissolved in dilute 

 hydrochloric acid, and the solution added to the volume of the extracts 

 previously obtained. This fluid was now evaporated on a water-bath to 

 complete dryness, and the residue then heated carefully, in order to convert 

 any ferric chloride present into ferric hydrate. A few drops of dilute 

 hydrochloric acid were added to dissoh^e all the magnesium salts present, 

 then the preparation was carefully evaporated and heated to expel all traces 

 of free acid. It was now dissolved in sufficient water to make the total 

 weight that of the plasma or serum taken, and the A of this solution was then 

 •determined. In the majority of cases, two such solutions were made from 

 two weighed portions of the same plasma or serum. 



The values of the A so obtained cannot be regarded as free from objection. 

 The solutes in such fluids are not under the same conditions as in the plasma 

 or serum. In the latter, their dissociation is diminished by the colloids 

 present. This, however, is compensated for in such solutions to a certain 

 extent, since, owing to the absence of colloids, there is a slightly greater 

 degree of dilution of solutes, and though there must, therefore, be a very 

 slight increase in dissociation, the depression of the freezing point must be 

 lessened. On the whole, consequently, while the values of the A ascertained 

 may not be absolutely accurate, they still are data which can be compared 

 with the values for the blood and serum. 



Such solutions were further employed when the quantity of the plasma or 

 serum was limited, as was the case with those fluids from the dog-fish and 

 the cod. In this case the material had to be so used as to permit of the 

 determination of as many constituents as possible. The ii'on in such 

 solutions was precipitated by the addition of strong acetic acid and some 

 ammonium phosphate, and from the filtrate ammonium oxalate precipitated 



