206 ANALYSIS OF THE GASES OF BLOOD. [BOOK I. 



In Fig. 45 the pump is shewn as fitted up for an actual 

 experiment ; between the pump and the blood-receiver a wide 

 glass bottle containing sulphuric acid and asbestos is shewn. All the 

 connections are protected by water or mercury joints. Standing in 

 front of the pump, and held by an iron clamp, is a tube similar to the 

 one which is only partiaUy seen in the drawing of the pump and its 

 connections. 



The Author's experiments with Alvergniat's pump have impressed 

 him most favourably. The smallness of the barometric chamber 

 naturally makes the process of exhausting the apparatus connected 

 with the pump a very tedious matter, unless the plan be adopted of 

 exhausting at first by means of an ordinary air-pump or with the aid 

 of a water aspirator, and towards the close of the exhaustion allowing 

 two or three cubic centimetres of boiled-out water to enter the 

 nearly empty bulb and heating the water which surrounds the bulb 

 so as to cause the contained water to boil. The steam which is 

 disengaged, very rapidly and perfectly expels the last traces of air. 

 Without this expedient the experimenter will almost despair to 

 obtain a good vacuum with Alvergniat's pump, when there are 

 connected with it vessels having a capacity of between 1500 and 

 2000 c.c. 



The Author has found it convenient to interpose a small sulphuric 

 acid chamber between the pump and the blood-receptacle, the object 

 being to prevent the passage of water into the former and from 

 it into the tube in which the gas is collected. With this addi- 

 tion he can recommend Alvergniat's pump as adapted for researches 

 on the gases of the blood 1 . By its portableness, it lends itself 

 admirably to demonstrations in the lecture-room. 



It will be found convenient to employ about 30 or 35 cubic 

 centimetres of blood for the determination of gases. The tem- 

 perature at which the process is best carried on is 45 C. By simply 

 heating in vacuo, the whole of the gases which are in a state of 

 solution or feebly combined may be removed ; the last portions of 

 carbonic acid are however more rapidly evolved by allowing a small 

 volume (one or two cubic centimetres) of a thoroughly boiled out 

 solution of phosphoric acid to enter the blood-receptacle near the close 

 of the operation. As has been shewn, however, by Pfliiger and his 

 pupils, the addition of an acid to blood before the oxygen has been 

 pumped out leads to a considerable diminution in the volume of 

 oxygen obtained, in consequence doubtless of the gas being used up 

 in processes of oxidation. 



ANALYSIS OF THE GASES OF THE BLOOD. 



It is not consistent with the object of this work to give detailed 

 descriptions of operations which belong to general chemistry, and 



1 This pump is manufactured by MM. Alvergniat freres, Kue de la Sorbonne, Paris. 

 It costs only 160 francs ; the tube with bulb, &c. being sold separately. 



