Speedy Volumetric Determination of Carbonic Acid. 181 



comma bacillus, and we would suggest to future observers that 

 possibly acid media may be found better suited for the growth of this 

 parasite. As to whether the micro-organism is frequently or con- 

 stantly present in the contents of the intestine, our cultivations as 

 above-mentioned are of no value. Nor does our examination of 

 stained films enable us to speak definitely for or against the presence 

 of this parasite. In the intestinal contents or the dejecta of cholera 

 cases, we have seen appearances which resembled in many points the 

 characters of the micro-organism in question ; none of our films, 

 however, show structures which are unmistaheably identical with 

 those found by us in the substance of the mucous membrane. 



We have only to add that not having cultivated this micro-organism 

 artificially, we claim no right to say that it is the cause of Asiatic 

 cholera. All we have to say is, that we have found it present in 

 certain tissues of all the cholera cases which we had the opportunity of 

 examining. Further investigation must decide whether or not it can 

 be looked upon as the direct cause of the disease. 



" An Instrument for the Speedy Volumetric Determination 

 of Carbonic Acid." By William Maroet, M.D., F.R.S. 

 Received June 9. Read June 10. Revised by the Author 

 June 29, 1886. 



[Plate 2.] 



The principle of this instrument is the absorption of carbonic acid 

 in a closed receiver by potassium hydrate, and the accurate measure- 

 ment of the volume of dry atmospheric air required to re-establish 

 the atmospheric pressure after complete absorption. The volume of 

 air used for that purpose will exactly correspond to that of the car- 

 bonic acid gas absorbed. It is obvious that whatever be the reading 

 of the barometer, the volume of air corresponding to that of the 

 carbonic acid absorbed, will give the correct proportion of carbonic 

 acid in the air submitted to analysis ; but to obtain the weight of the 

 gas present, and its proportion by weight, it will be necessary to 

 reduce both the volumes of air analysed and of carbonic acid found 

 to their volume at 0° (C), and under a pressure of 760 mm. of 

 mercury. Hence the necessity of recording the height of the baro- 

 meter at the time of the experiment, or one reading may suffice for 

 a number of determinations. 



The instrument resembles two small gasometers, and consists of two 

 tanks and two bell- jars, or air-holders, each of the latter being made 

 to hold half a cubic foot of air. The bell- jars hang on a metallic cord 

 which connects them with each other, and passes over two pulleys, 



