232 RED PARTICLES 



in the blood of different animals. And as both a very strong 

 solution of neutral salts and a very diluted one alters the 

 shape of the vesicles, it is probable nature has limited the 

 proportions of the water and the salts in our blood. 



A degree of latitude in these proportions, however, seems 

 to be admitted, for I observed the vesicles equally unchanged 

 when mixed with a solution of salts, consisting of eight drops 

 of water to one of the saturated solution. And when added 

 to a mixture of fifteen drops of water to one of the same solu- 

 tion, not only the neutral salts in the blood are capable of 

 preventing the serum from dissolving the vesicles, 'but the 

 mucilage (cxiv), or lymph, with which the serum- is so much 

 impregnated, seems to contribute to the same effect. 



When the vesicles have been made spherical by being mixed 

 with water, if a small quantity of a pretty strong solution of a 

 neutral salt be added, they are immediately shrivelled; a few 

 of them recover their former flat shape, but the greatest part 

 are contracted irregularly into small spheres. When these 

 vesicles thus recover their shape, after having been a short 

 time mixed with water, they are generally more transparent, 

 and appear thinner, a part of their substance having been dis- 

 solved in water, and thence it is more easy to distinguish 

 the little solid particle which is contained in them. By this 

 experiment I have had the pleasure of convincing many curious 

 persons of the composition of this part of the blood, who were 

 not quite satisfied from some of the other experiments. 



I have mentioned above, and shown in Plate V, that these 

 vtoicles are of different sizes in. different animals. I have like- 

 wise observed, that they are not all of the same size in the 



(cxiv.) Coagulable lymph was by many of the older writers called 

 mucilage the mucago of Harvey a , and in that sense the word may 

 have been familiar in Hewson's time. In the First Part of these 

 Experimental Inquiries, pp. 78, 79, and 80, he employs the term muci- 

 lage for the coagulable matter of the serum. Synovia was said to be an 

 example of animal mucilage. 5 Verduc c states that the coagulation of 

 the blood is owing to a mucilage mixed with the red part. 



a De Generatione Animalium, pp. 160-1, de Physiologic, torn, ii, p. 565, and 



Exer. 51, 4to, Lond. 1651. torn, i, p. 724, 8vo, Paris, 1766. 



b Dictionnaire Raisonne d'Anatomie et c Traite de TUsage des Parties, 12mo, 



Paris, 1696, t. i, pp. 184-5. ' 



