704 SPECIAL HISTOLOGY. 



of the globules in accurately determined quantities of blood, and as pre- 

 cise a determination as possible of the volume of the individual corpus- 

 cles (Vierordt) ; but this method, if applied in such a way as to insure 

 correct results, demands so much time and trouble, that it cannot be 

 expected to obtain general application, and we must be contented with 

 an accurate investigation of the total quantity of blood-globules in a 

 single or in some few instances, an undertaking in which Vierordt is now 

 engaged.* 



The red blood-globules, more minutely examined, present the follow- 

 ing characters : Their form is usually that of a biconcave or plane, 

 orbicular disk, with rounded borders, and consequently they present a 

 different aspect to the observer, according as the surfaces or borders are 

 turned towards him. In the former case they are pale yellow, orbicular 

 corpuscles, in which, according to the focussing of the microscope, the 

 slight central depression which almost always exists, is indicated, some- 

 times by a clear, sometimes by an opaque spot in the centre, the latter 

 appearance admitting of being confounded with a nucleus. Viewed on 

 the edge, on the other hand, they present the form of an elongated, 

 narrow ellipse, or of an ellipse constricted in the middle. The blood- 

 corpuscle is constituted of a very delicate, but nevertheless tolerably 

 firm, and at the same time, elastic, colorless cell-membrane, composed 

 of a protein substance closely allied io fibrin, and of colored viscid con- 

 tents formed of globulin and Jicematin, which in the adult present no 

 trace of morphological particles, of granules, or of a cell-nucleus; they 



• [Vierordt's method, as lately published by him ("Schmidt's Jahrb.'' 4, 1S52) consists 

 in an actual enumeration of the blood-corpuscles, when mixed with fluids of a certain den- 

 sity. His mode of procedure is to take up a small quantity of blood by a capillary tube of 

 uniform size. The length of the blood-column in the tube is measured under a low mag- 

 nifying power, and multiplied by the diameter of the tube; and thus the total volume of the 

 blood-column is obtained. The blood is then allowed to run from the tube on to a glass slide, 

 is there spread out in narrow streaks, and intimately mixed with a solution of gum, or 

 albumen. The blood-streaks are successively brought under the divisions of an ocular 

 micrometer, and the number of corpuscles in each accurately counted. This process will 

 enable us to determine, with tolerable accuracy, the number of corpuscles in a certain quan- 

 tity of blood. It is, however, extremely laborious, since Vierordt himself states, that in 

 order to complete a single enumeration, nearly one \^-eek is required. 



A mode of procedure by which the number of the blood-corpuscles may be more readily 

 ascertained, is the one proposed by Welcker (Archiv. des Vereins. fiir. Gem. Arb. B. 1, H, 2, 

 1853). This observer employs a stage micrometer, divided into a known number of paral- 

 lelograms. On this, the blood, mixed with a solution of albumen, is spread, and the corpus- 

 cles in each division counted, with the aid of an ocular micrometer. For practical purposes, 

 Welcker states that the number of the blood-corjiuscles maybe ascertained by a yet simpler 

 method. A measured quantity of blood is diluted with a certain quantity of fluid, the color 

 of the diluted blood is then compared with a color scale determined upon by previous ex- 

 periment, and by the degree of color, the number of the blood-corpuscles may be approxi- 

 mately estimated. By employing both these methods, Welcker was able to ascertain that 

 healthy blood (his own) contained about 4,000,000 corpuscles in a cubic millimetre, whilst 

 in a case of hysteria he found but 3,800,000, and in a patient in the last stage of consump- 

 tion, but 2,400,000 corpuscles.— DaC] 



