CHAP. III.] THE BLOOD IN DISEASE. 147 



variation which the weight of the moist corpuscles undergoes in respect to 

 the weight of the liquor sanguinis, in various diseases. The methods 

 which we possess for effecting this determination with accuracy are, 

 however, so complex and so difficult, that no large collection of data 

 directly obtained by this method exists. We can, however, as was shewn 

 by the researches of C. Schmidt, obtain a very close approximation to the 

 true weight of the moist blood-corpuscles present in the blood, if we 

 multiply the results obtained by Prevost and Dumas' method (which 

 was employed by Becquerel and Rodier in their researches) by 4. 



Since, however, methods have been devised (1) for the enumeration of 

 the blood-corpuscles contained in a known volume of blood and (2) for the 

 determination of the amount of haemoglobin, the physician has been placed in 

 possession of methods which have thrown great light upon some of the 

 diseases in which the blood-corpuscles are diminished in which typically 

 the condition of anaemia exists. 



By means of any of the methods described at pages 74 78 a close 

 approximation to the number of corpuscles contained in the blood may be 

 made in a few minutes, by employing a single drop of blood. Similarly 

 by methods as ready and as accurate, the amount of haemoglobin in the 

 blood may be determined. 



As we have seen, haemoglobin constitutes by far the most abundant 

 constituent of the red blood-corpuscles, and it might be supposed that the 

 second of the above determinations might be sufficient for the purposes of 

 the physician ; the richness or poverty of the blood in coloured corpuscles 

 being judged of by its richness or poverty in haemoglobin. Such is 

 however not the case, as will be now briefly shewn. 



Changes It resulted from the labours of Welcker, the dis- 



coverer of all the fundamental facts concerning the 

 corpuscles , , . . , . , . ., P . & , 



undergo in relative number, weight, cubic capacity, superficies and 



Anaemia. colouration of the blood-corpuscles, that in the physio- 



logical condition the colour of the blood is proportionate to the 

 number of its coloured corpuscles in other words, that in the 

 healthy state the amount of haemoglobin contained in the red 

 blood-corpuscles is constant. That Welcker was correct in his statement, 

 in so far as the healthy state is concerned, has been proved by the recent 

 researches of Worm-Muller 1 , and is, on the whole, confirmed by Malas- 

 sez 2 . In his remarkable researches on the changes which the blood 

 undergoes in cholera and some other diseases, C. Schmidt 3 had how- 

 ever pointed out that the composition of the blood-corpuscles is liable 

 to vary in disease, and attention was still more forcibly drawn to 

 this interesting fact by Johann Duncan in 1867 4 . This observer 



1 Worm-Muller, "Ueber das Verhaltniss zwischen der Zahl der Blutkorperchen 

 und der Farbekraft des Blutes." Om Forholdet imellem Blodlegemernes Antal og Blodets 

 Faroekraft. Christiania, 1876. Abstracted in Maly's Jahresbericht, Vol. vii. (1878), 

 p. 102. * 



3 Malassez, " Sur les diverges methodes de dosage de 1'he'moglobine et sur un 

 nouveau colori metre." Archives de Physiologic, Ser. n., Vol. iv. (1877), pp. 1 13. 



3 C. Schmidt, Charakteristik der epidemischen Cholera, &c. 



4 Duncan, " Beitrage zur Pathologic und Therapie der Chlorose." Sitzungsber. d. 

 kais. Akad. d. Wissenschaften zu Wien. Naturwissenschaft. Cl. 1867. 2 Abth., pp. 

 516522. 



102 



