THE ALUMNI JOURNAL. 



63 



THE HOST RECENT WORK. 



Action of Carbonic Oxide on Man. — 

 The experiments made by the author J. 

 S. Haldine, on himself, show that the 

 symptoms caused by carbonic oxide de- 

 pend on the extent to which the Haemo- 

 globin has been saturated; the percent- 

 age saturation of the Haemoglobin of the 

 red corpuscles may be estimated during 

 life by a simple colorimetric method. 

 Carbonic oxide is a "cumulative" poison. 

 The symptoms do not become sensible 

 during rest until the corpuscles are about 

 one-third saturated; with half saturation, 

 the symptoms (respirator37 distress, head- 

 ache, etc.), become urgent. 



Similar symptoms are experienced by 

 mountaineers at high attitudes. 



When air containing this gas is breath- 

 ed, about half of that actually inhaled is 

 absorbed, except when absorption is 

 coming to a standstill. 



The time required for the production 

 of sensible symptoms in an adult depends 

 on the time required for the inhalation of 

 about 660 cc, or the absorption or about 

 330 cc. of the pure gas; this time in dif- 

 ferent animals varies with the respera- 

 tory exchange per unit of body weight 

 and is about 20 times as long as in man 

 as in a mouse; hence, a mouse can be 

 used as an indicator in a coal mine before 

 men penetrate into it. 



The maximum amount of carbonic ox- 

 ide capable of being absorbed by the blood 

 from air containing a given small percent- 

 age, depends on the relative affinities of ox- 

 ygen and carbonic oxide for Haemoglobin , 

 and the relative tension of the two gases 

 arterial blood. The affinity of carbonic 

 oxide for Haemoglobin, is about 140 

 times that of oxygen, and the oxygen 

 tension of human arterial blood is, ap- 

 proximately 16 per cent, of an atmo- 

 sphere. 



Distinct symptoms, appreciable dur- 



ing rest, are not produced until about 

 0.05 per cent, of the gas is present, with 

 about 0.2 per cent, urgent symptoms are 

 produced. With a given percentage of 

 carbonic oxide in air, a certain percent- 

 age of saturation of the blood is reached 

 within about 150 minutes, and is not 

 afterwards exceeded, however long the 

 breathing of the vitiated air is continued. 



The disappearance of the gas from the 

 blood when fresh air is again breathed, 

 is always much slower than the absorp- 

 tion of the gas, and is chiefly due to dis- 

 sociation of carbonylhaemoglobin by the 

 mass influence of the oxygen in the pul- 

 monary capillaries, and the consequent 

 diffusion of the gas outward through the 

 alveolar epithelium. — (/. Physiol, 1895, 

 18, 430-462). 



Finiction of Diastase in Plants. — Dias- 

 tase may be readily detected in the cells 

 of plants by digesting the tissue, for a 

 sufficient length of time, with a solution 

 ofguaiacumin absolute alcohol, and then 

 immersing sections of it in a dilute solu- 

 tion of hydrogen peroxide ; a fine blue 

 color is developed in those cells which 

 contain the enzyme. The author (J. 

 Griiss) finds that diastase is always 

 present in those parts of the plant from 

 which it is necessary that starch should 

 be removed for purposes of nutrition. As 

 the amylolytic power of diastase is in- 

 hibited by the presence of more than a 

 certain limited amount of glucose it would 

 seem that in assimilation the formation 

 of glucose precedes that of starch, and 

 continues as long as the sugar is remov- 

 ed by circulation. When, however, the 

 sugar commences to accumulate beyond 

 the requirements of the organism, it un- 

 dergoes polymerisation to maltose and 

 eventually to starch, which, in the pres- 

 ence of glucose, is not hydrolyzed b}^ the 

 diastase ; as soon, however, as the glu- 

 cose is reduced by circulation below the 



