ON THE UNION OF TAN AND JELLY. ] 1 



precipitating jelly. The water exhibited a reddiih tinge, 

 and was also slightly affected by the addition of iron, show- 

 ing, that it contained a minute portion of gallic acid ; no 

 effect was, however, produced on it by the muriate of tin. 

 The boiled precipitate now approached in its appearance to 

 the one which was composed of equal parts of tan and jelly ; 

 it was of a deeper colour and harder consistence. The first 

 of these three precipitates was boiled in the same manner 

 that this third had been, but the water was not in the least 

 degree affected by jelly. It may appear singular, that any 

 part of a substance, which had been precipitated from 

 water, should be dissolved by it, but it probably depends 

 upon the action of the greater mass of the fluid ; and the 

 fact is confirmed by Mr. Davy's remark, that the stronger 

 the solutions are upon which we operate, the more complete- 

 ly will their solid contents be separated from them. 



From the foregoing observations and experiments we may Accurate re- 

 infer, that the method of detecting the quantity of jelly in suits not to be 

 any fluid, by the precipitate which it forms with tan, cannot thi? process. 

 be employed with any prospect of obtaining accurate re- 

 sults ; nor can jelly be depended upon for the purpose of 

 obtaining the amount of the tan in any astringent vegeta- 

 ble infusion. In the animal analysis this deficiency will 

 probably be found of little importance; for, notwithstand- 

 ing the proportion of jelly which enters into our solids, afcd 

 which may be readily extracted from them by water, I am No jelly in the 

 inclined to believe, that nothing, which is properly entitled animal fluids, 

 to the name of jelly, will be found to exist in any of our 

 fluids. When I first began these investigations I was in- 

 duced to form a contrary opinion, and a contrary doctrine is 

 maintained in our most valuable systematic works. I have, 

 however, endeavoured to prove, that jelly is not found in 

 the blood, where it has been supposed to exist in the largest 

 quantity*; 1 do not find any trace of it in the albumen ovi, 

 in the saliva, in the fluid of the hydrocephalus, of spina bi- 

 fida, or of ascites, nor in the liquor amnii. By far the 

 largest proportion of animal matter in all these fluids is al- but albumen, 

 bumen, existing sometimes in its coagulated, and sometimes 



• Medico-chirurgical Trans. V. I, p. 47. 



