50 STUDIES ()> FEllMENTATIOX. 



expected, the direct oxidation of the constituents of blood by 

 slow combustion was rather sluggish. After subjecting our 

 flasks to a temperature of 25^ C. or 30° C. (77° F. to 80° F.) in 

 an oven for several weeks, we observed an absorption of not 

 mora than 2 or 3 per cent, of oxygen, which was replaced by 

 a volume of carbonic acid gas of about an equal bulk.* 



Nearly the same results were obtained in the case of urine ; 

 it underwent no radical change ; its colour merely assumed a 

 reddish brown tint ; it formed some small deposirs of crystals, 

 but without becoming at all turbid or putrefying in any way. 

 The direct oxidation of the urinary substances was likewise 

 very sluggish. An analysis of the air in one of the flasks, 

 made , forty days after the commencement of the experiment, 

 gave the following results : — 



Oxygen . . . . . . . . 19-2 



Carbonic acid.. .. ., .. 0-8 



Nitrogen 80-0 



100-0 



* We must mention one curious result, which relates to what have 

 been called the crystals of the blood. We could hardly have recourse to a 

 better method of preparing these crystals, at least in the case of dog's 

 blood, which seems to yield them with the greatest facility in any quan- 

 tity we might desire to procure. Under the circumstances just recounted, 

 in which dog's blood exposed to contact with pure air underwent no 

 putrefactive change whatever, the crystals of that blood formed with a 

 remarkable rapidity. From the first day that it was placed in the oven 

 and exposed to an ordinary temperature, the serum began gradually to 

 assume a dark brown hue. In proportion as this effect was produced, 

 the globules of blood disappeared, and the serum and the coagulum 

 became filled with very distinct crj^stals, of a brown or red colour. In 

 the course of a few weeks, not a single globule of blood remained, either 

 in the serum or coagulum ; every drop of serum contained thousands of 

 these crystals, and the smallest particle of coagulum, when bruised under 

 a piece of glass, presented to view coloux-less and very elastic fibrine, 

 associated with masses of crj^stals, without the slightest trace of blood- 

 globules. Where our observations were protracted, it sometimes hap- 

 pened that all the fibrine collected into one hyaline mass, which gradually 

 expelled every crystal from its interior. 



