280 Prof. Wright. Influence of Carbonic Acid and [Mar. 15, 



differs from the method previously described by Vierordt* in the 

 following particulars : 1. A series of capillary tubes, of equal calibre, 

 is employed instead of the single capillary tube employed by Vierordt. 

 2. Coagulation time is determined by blowing down the capillary 

 tubes, one after another, at regularly increasing intervals until a tube 

 is found to have become blocked by clot. In Vierordt's method the 

 occurrence and duration of coagulation is judged of by passing a 

 chemically cleansed white horse-hair down the capillary tube, and 

 observing the deposition of coagulum upon its surface. 



In all cases I employed a column of blood of 5 cm. in length, and 

 received it into tubesf which had a diameter of approximately 

 0-25 mm. 



The following precautions were observed in order to ensure accu- 

 racy of results : 1. The coagulation tubes were washed out before 

 use successively with distilled water, absolute alcohol, and ether. 



2. They were then warmed in an incubator to a temperature of 37 C. 



3. A fresh drop of blood was employed for filling each tube. 4. The 

 column of blood was aspirated some little distance up the tubes to 

 prevent desiccation occurring at the orifice. 5. In testing for coagu- 

 lation the blood was blown out on to a piece of white filter paper in 

 order to ensure the detection of the first traces of clot. 



The gases which were experimented with were the following : 

 Atmospheric air, oxygen, hydrogen, carbonic acid, and a mixture of 

 (approximately) 20 per cent, of oxygen with 80 per cent, of carbonic 

 acid. I also examined the effect of clamping the trachea. 



Effect of an Increase of Carbonic Add. 



In order to elicit the effect of an increase of carbonic acid upon 

 coagulability, I caused the animals to inspire out of a reservoir con- 

 taining a mixture of 1 part (approximately) of oxygen with 4 

 of carbonic acid. This mixture of gases presents the obvious ad- 

 vantage of supplying carbonic acid in association with the normal 

 quantum of oxygen. Determinations of blood coagulability were 

 made when the animals were breathing this mixture of gases, 

 the results were compared with the " coagulation times " which we 

 elicited immediately before when the animals were breathing atmc 

 spheric air. Thirty experiments were made. Out of these twenty- 

 seven showed a marked increase^ of coagulability while the animal 

 vras breathing the mixture of carbonic acid and oxygen. In two ex- 

 periments coagulation time was unaltered, and only in one exj 

 ment was a slight diminution of coagulability observed. 



* ' Archiv fur Heilkunde,' 1878. 

 t These tubes were supplied by Mr. A. E. Dean, Jua., 73, Hatton Garden E.C. 

 J This increase of coagulability is well shown in the first ten of the protocols 

 appended to this paper. 



