CHAP. IV.] THE BLOOD. METHODS OF RESEARCH. 203 



off the upper part of the blood-bulb from the drying-chamber and the 

 barometric chamber of the pump are opened. The blood-bulb M is now 

 immersed in a vessel containing water at 40 C., when the blood enters 

 into violent ebullition : if arterial in colour before being introduced into 

 the bulb, it assumes almost instantly the cherry-red colour which is 

 characteristic of reduced haemoglobin; if the reddened walls of the 

 froth-chamber be viewed through a spectroscope the simple broad band of 

 reduced haemoglobin is then seen. After a few minutes the gases which 

 have been given off are collected over mercury in a tube filled with 

 mercury, the vacuum is renewed, and the process of ebullition continued. 



Some observers who have used the pump shewn in Fig. 42, have 

 determined the amount of blood analysed, by actually weighing it. With 

 this object, the exhausted and empty blood-bulb is detached from the pump 

 and weighed ; thereafter the quantity of blood to be analysed is introduced 

 into it, in the manner previously mentioned ; the stop-cock M through 

 which blood has flowed is then rinsed, first with water, then with alcohol, 

 and rapidly dried, and the bulb is again weighed. The blood bulb is then 

 again joined to the bulbs A (Fig. 42), of which the stop-cock N has been 

 kept closed. The junction having been made, the small quantity of air 

 which intervened between the upper stop-cock of the blood-bulb and N 

 having been removed by a few strokes of the pump, the process of boiling 

 the bulb is commenced. This process appears to the Author to be tedious 

 and unsatisfactory in the extreme. It is always better to pass the blood 

 from an apparatus in which it is first measured to the blood-bulb ; it is 

 indeed quite practicable to measure the blood and pass it into the bulb, 

 before coagulation has had time to set in. 



In the mercurial pumps made by Geissler of Bonn, and which are, 

 the Author believes, identical with those used by Professor Pfliiger himself, 

 the arrangement shewn in Fig. 44 is employed. 



FIG. 44. LARGE RECEIVER or PFLUGER'S PUMP, AS MADE BY GEISSLER OF BONN, 



INTO WHICH BLOOD IS INTRODUCED, AND BOILED FOR THE EXTRACTION OF ITS GASES. 



The tube which conveys the blood to be analysed is slipped over A. 

 By suitable manipulation of the stop-cock, the blood is first made to expel 

 the air in the tube A, outwards through 0. The blood may then be directed 



