26 SPECIFIC GRAVITY AND REACTION OF BLOOD. [BOOK I. 



upon the chemical relations of the colouring matter to oxygen, though 

 in part also upon the shape of the coloured blood corpuscles, which is 

 subject to various physical influences. 



The specific gravity of the living blood cannot for obvious reasons 

 be ascertained ; that of defibrinated human blood drawn from 

 healthy subjects has been found to vary between 1045 and 1062 *, 

 the average being 1055 ; greater variations than are indicated by 

 the above numbers are however consistent with health, the widest 

 limits being probably indicated by the numbers 1045 1075. 



The mean specific gravity of the blood of the dog was found by 

 Pfluger to be 1060 2 , and by Nasse to be 1059 3 ; that of the blood of 

 the rabbit was found by Gscheidlen to vary in three cases between 

 1042 and 1052. 



As blood is drawn from a vessel it is found to vary slightly in 

 density, that drawn first having a somewhat higher specific gravity 

 than that which follows, owing to the quantity of water of the blood 

 increasing as a result of haemorrhage 4 . 



Reaction. Blood always possesses a feebly alkaline reaction, which 

 rapidly diminishes from the time of its being shed to the time of its 

 coagulation. 



The red colouring matter of the blood interferes with the ready determina- 

 tion of the reaction as by simply immersing ordinary test-papers into the 

 fluid, and therefore one or other of the three following methods may be 

 employed, of which the second and third, b and c, are to be preferred. 



(a) Kuhne's Method 5 consists in placing a drop of blood in a 

 specially constructed tiny dialyzer of parchment-paper; this is then immersed 

 in a drop of water contained in a watch-glass. After a short interval the 

 reaction of the water is determined by means of litmus paper. 



(b) Liebreich's Method . Plaster of Paris absolutely free from 

 alkaline reaction is cast into thin slabs, which are then dried, and 

 afterwards coloured by dropping upon them a perfectly neutral solution of 

 litmus. When a droplet of blood is allowed to fall upon the coloured slab, 

 the fluid of the drop is soon absorbed by the porous gypsum whilst 

 the corpuscles are left. On placing the spot under a stream of water, 

 the corpuscles are washed away and the colour of the slab at the 

 site of the blood spot is found to be a more or less deep blue. 



(c) Zuntz's Method 7 . This method rests upon the fact that the 



1 Becquerel et Rodier, Recherches sur les alterations du sang. Paris, 1844. 

 3 Pfluger, "Ueber die Ursache der Athembewegungen, sowie der Dyspnoe und 

 Apnoe." Archiv d. gesammten Physiologic. Bd. i. (1868) p. 75. 



3 Nasse, Haematologische Mittheilungen. Quoted by Gscheidlen, Physiologische 

 HethodiTc, p. 328. 



4 Becquerel et Rodier, Traite de Chimie Paihologique, appliquee d la Medecine pra- 

 tique. Paris, 1854, p. 41 et seq. 



& Kuhne, "Ein einfaches Verfahren, die Reaction hamoglobinhaltiger Fliissig- 

 keiten zu priifen." Virchow's Archiv, vol. xxxui. (1865), p. 95. 



6 Liebreich, " Eine Methode zur Priifung der Reaction thierischer Gewebe. " Berichte 

 d. deutschen c/iem. Gesellsch. zu Berlin, 1868, p. 48. 



7 Zuntz, Centralblatt, 1867, ' No. 34. See also Adam Schulte, Ueber den Einflms 

 des Chinin auf einen Oxydatioiuprocess im Blute. Inaugural Dissertation. Bonn, 1870. 

 p. 9 et seq. 



