24 THE J3L00D. 



from the mass and move freely in the liquid (Osier).* Masses of pig- 

 mentous matter are also occasionally found, especially in disease ; and 

 in the blood of the splenic vein cells enclosing red blood-corpuscles 

 have been noticed (Ecker, KuUiker). Fine interlacing filaments are 

 commonly to be seen in a preparation of blood under the microscope. 

 These consist of fibrin, and are formed, after the blood has been drawn, 

 in the manner to be presently noticed. 



Liquor Sanguinis, or Plasma. — This is the pale clear fluid in 

 which the corpuscles are naturally immersed. Its great character is 

 its strong tendency to coagulate when the blood is withdrawn from the 

 circulating current, and on this account it is difficult to procure it free 

 from the corpuscles. Nevertheless, by filtering the slowly coagulable 

 blood of the frog, as was first practised by J. Miiller, the large corpuscles 

 are retained by the filter, while the liquor sanguinis comes through in 

 perfectly clear and colourless drops, Avhich, while yet clinging to the 

 funnel, or after they have fallen into the recipient, separate into a 

 pellucid glassy film of fibrin, and an equally transjiarent diffluent 

 serum. When human blood is drawn in inflammatory diseases, as well 

 as in some other conditions of the system, the red particles separate 

 from the liquor sanguinis before coagulation, and leave the upper part 

 of the liquid clear. In this case, however, the plasma is still mixed 

 with the pale corpuscles, which, being light, accumulate at the top. On 

 coagulation taking place in these circumstances, the upper part of the 

 clot remains free from redness, and forms the Avell-known buify coat so 

 apt to appear in inflammatory blood. Horse's blood ordinarily presents 

 this condition when drawn. 



The readiest way to obtain the liquor sanguinis in quantity free from red 

 corpuscles is to allow the blood of the horse to flow from the vessels into a 

 receiver, kept cool by means of ice : the blood corpuscles sink to the bottom, 

 leaving the upper part of the fluid clear and colourless. This may be drawn 

 off into another vessel and is found readily to coagulate at a slight elevation of 

 temperature. In the case of frog's blood this artificial cooling is not always 

 necessary ; for, if it be collected with as little disturbance as possible, f.g., if the 

 heart be allowed to pump blood directly into a clean glass tube, little or no 

 coagulation may take place, so that the corpuscles rapidly subside and leave the 

 plasma perfectly clear and colourless.^ In jfost mortem examinations the ca^dties 

 of the heart are often found occupied by an almost completely coloui'less, gela- 

 tinous coagulum. This is due to the subsidence of tlie corpuscles after death. 



Coagulated plasma, whether obtained from buflpy blood, or exuded on 

 inflamed surfaces, presents, under the microscope, a multitude of fine 

 filaments confusedly interwoven, as iu a piece of felt ; but these are 

 move or less obscured by the intermixture of corpuscles and fine 

 granules, the former having all the characters of the pale corpuscles of 

 the blood. The filaments are no doubt formed by the fibrin, as it 

 solidifies in the coagulation of the liquor sanguinis. Sometimes, how- 

 ever, fibrin presents when coagulated a gelatinous appearance under the 

 microscope without any sign of filaments. 



Blood may be freed from fibrin by stirring it with a bundle of twigs, 

 which entangle the fibrin as it concretes. 



* Centralblatt f. cl. med. Wissensch. 1873. Proc. R. S., 1874. 

 + Schafer. British Association Reports, 1872. 



