74 COLOURED CORPUSCLES. THEIR ENUMERATION. [BOOK I. 



To day, this simple notion is enlarged into the doctrine of the 'stroma.' 

 The red blood cell consists of a cavernous mass or 'stroma,' denser at 

 the periphery than at the centre, whose external limit or boundary appears 

 as a sharp contour. It is colourless and highly elastic : it is albuminous 

 in substance, and generally admitted to be non-contractile. In the central 

 trabeculae of the mass the nucleus is embedded, in those red corpuscles 

 which are nucleated. The interstices are quite filled by the coloured 

 substance of the corpuscle, which, under certain conditions (e.g. cautious 

 irrigation with water, or with boracic acid of 2 p.c.), retreats from the edge 

 upon the centre in a more or less regular manner. The stroma has 

 been called by Briicke the oekoid, and the contained coloured matter the 

 zooid. The special appearances upon which this view is founded have 

 already been stated. The view is not inconsistent with any of the known 

 reactions of blood corpuscles ; and it is especially adapted to interpret the 

 concentration of the zooid in the interior of the oekoid l . 



Enumeration of the corpuscles. 



Principle It might at first appear hopeless to attempt to 



^th^ 110 ^ 3 ^ count the number of the blood corpuscles in the 

 enumeration blood, especially when we mention at the outset that 

 are based. one cubic millimetre of blood is estimated to contain 



about 5 millions of corpuscles. But the possibility of 

 carrying out the process so as to permit of a fair approximation 

 becomes evident so soon as the principle is grasped, upon which all 

 the methods are based, all being but modifications of the method 

 suggested by Vierordt and first carried out in all detail by that 

 observer and by Welcker, whose results have received full confirma- 

 tion by the numerous researches carried on by the aid of the more 

 easy methods of Malassez, Gowers, &c. 



The principle, then, is to dilute a known volume of blood with a 

 sufficient but definite and known quantity (say 100 times its volume) 

 of some colourless transparent solution which will not destroy the 

 blood corpuscles, and which will affect their shape as little as possible ; 

 thereafter to take a known and very minute volume of the diluted 

 blood, and with the aid of suitable micrometric arrangements to 

 count the corpuscles in it. 



The methods will now be described in detail. 



Vierordt "A measured volume of blood is diffused as equably 



and Welcker's as possible in a thousand times its volume of an indifferent 

 method . fluid (six grammes of NaCl in one litre of water, according 



to Welcker). A small quantity of the mixture is taken up in a capillary 

 tube of known calibre, and the length of the thread of fluid is estimated 

 under the microscope by means of a micrometer. When the contents 

 of the tubule have thus been ascertained, they are quickly distributed 



1 For fuller information the student is referred to the article on "Blood" by Pro- 

 fessor Rollett, in Strieker's Handbook. 



2 Welcker, " Grosse, Zahl, Volum, Oberflache, und Farbe der Blutkorperchen bei 

 Menschen und bei Thieren." Henle u. Pfeufer's Zeitochrift fur rat. Medicin, Dritte 

 Reihe, VoL xx. Heft 1 and 2, page 257. 



