288 
Proceedings of Poyal Society of Edinburgh. [sess. 
On the Blood of the Invertebrata. By Dr A. B. Griffiths, 
F.B.S.E., F.C.S., Ac. 
(Read 1st June 1891.) 
I. The Gases of the Blood . — As very little is known concerning the 
composition and nature of the gases in the blood of the Invertebrata , 
the following notes may he of some value. 
The author has ascertained the approximate composition of the 
gases in the blood of certain Invertebrate animals. The apparatus 
used for this purpose was that of Gautier slightly modified (fig. 1) ; 
and the method allows the collection of the blood in vacuo (from 
the time of leaving the vein, &c.) without any alteration in its 
composition. The glass receiver ACD (left-hand figure), in which 
the vacuum is made, has a canula E fastened to its lower end. The 
canula is drawn out into a fine capillary point, which is pushed 
into the artery, vein, or under the hypodermis, as the case may be. 
After introducing the canula into the blood system, the tap B is 
opened and the blood rises into the receiver. The gases are 
evolved almost immediately, and by means of the pump they 
are collected over mercury in the tube ab , where their composition 
is ascertained. 
After the introduction of the blood into the receiver the tap B is 
turned off ; the receiver is then attached to the pump. Before 
opening the tap A, the receiver is placed in a bath of water heated 
to about 40° C. The heat assists in the liberation of the gases from 
the blood. Coagulation is prevented by previously introducing a 
small quantity of sodium chloride into the receiver (i.e., before the 
introduction of the blood).* 
The pump and pneumatic trough do not require description, as 
they are of the usual kind. The volume of the mixed gases collected 
in ab having been ascertained, the percentage of each gas is 
estimated by the ordinary methods of gas analysis. The carbonic 
* The liberation of carbonic anhydride is accelerated by previously intro- 
ducing into the receiver a small quantity of a hot solution of tartaric acid. 
