xxx INTRODUCTION. 



intermixed serum. Distinct from this fluid, these eminent men 

 had no knowledge of the coagulable lymph ; the same remark 

 applies to most of the British writers just mentioned ; and, like 

 some of them, Haller and Marherr believed that the buffy coat 

 is caused by a change in the serum. Schwenke 1 supposed the 

 nature of that crust to be intermediate to the serum and cruor; 

 and Gaber, 2 even while attesting the identity of the crust with 

 the matter left after washing the blood-clot and with Ruysch's 

 membrane, speaks of them as identical with the coagulable 

 matter of the serum, quoting, in support of this opinion, 

 Sauvages, de Haen, and Quesnay. Yet Marherr, amid the 

 vagueness in which he joined, after referring to the opinion of 

 those who held that there is a fibrous matter in the blood, more 

 correctly states that the fibres, when obtained by washing from 

 the clot, are formed from particles which were previously fluid. 

 Errors similar to those above noticed are contained in the 

 ' Dictionnaire Raisonne d'Anatomie et de Physiologic/ torn, ii, 

 pp. 381 and 384, 8vo, published at Paris in 1766. While such 

 were the current opinions, there were some writers, now to be 

 noticed, who had a clearer knowledge of the blood. 



Petit 3 declared it to be generally known, that all the parts 

 of the blood are not susceptible of coagulation ; that it at first 

 coagulates entirely, but after a while the serum separates from 

 the clot, as whey does from curdled milk. He always uses the 

 term serosity for the serum, as Verduc before and many other 

 writers afterwards did. After stating that this is not the 

 coagulable part, he says that the next parts are the lymphatic 

 and the globular ; and then gives a just view of the disposition 

 of the several parts of the blood in the heart and great vessels 

 after death, distinguishing the white and lighter clot of lymph 

 from the red and heavier globular part, and so accurately de- 

 ducing the effect that the position of the body after death 

 has on their relative situation. 4 In bleeding from the foot, he 

 described the diffusion of the colouring matter throughout the 

 water, and the separation of the white part. He declared 



1 Haematologia, p. 158, 8vo, Hagae Com. 1743. 



2 Melanges de Philosophic et de Mathematique de la Societe Royale de Turin, pour 

 les annees 1762-1765, pp. 167, 168, 170-72, 4to, 1766. 



3 Histoire de 1' Academic Royale des Sciences, ann. 1732, pp. 392-96, 4to, Paris, 

 1735. 4 See Note xin, pp. 23-4. 



