PRIMARY ANIMAL FLriDS. 25 1 



No effe^ was produced by adding the oxymurlafe of m'er- »— n«r by ox. m, 



cury to the ftandard iolution. The nitrate of iilver and the °^"?f^- ^o*""- 



J of lilv. norn. 



nitro-muriate of tin were each employed, and produced a very m.of tin. 



flight and almoft imperceptible opacity. 



The addition of the nitro-muriate of gold caufed a fmall N. m. of goU 



quantity of a denfe precipitate when added to the ftandard fo-^^^^ precip* 



lution; but when this was fo far diluted as to contain one grain 



of jelly in 500 of water, the eifedt was no longer perceptible. 



AIucus, 



Animal mucus or mucilage enters largely into the conftilu- Mucus ; a term 

 tion of many parts of the body, and forms a confiderable pro- "^^f^^j J," ^^ 

 portion of feveral of the fecretions. The terra mucus had mifts. 

 been generally employed in a vague and unreftri6led fenfe^ 

 until Mr. Hatchet, in his valuable paper on the membranous 

 parts of animals, inferted in the Phil. Tranf. for J 800, at- 

 tempted to affign to it a more appropriate and definite mean- 

 ing. He conceives that jelly and mucus are only modifications 

 of the fame fubftance, and do not elTentially differ from each 

 other; he confiders it to be entitled to the appellation of 

 mucus, when it is foluble in cold water and cannot be brought 

 to the gelatinous ftate *. Dr. Thomfon adopts in general the 

 idea of Mr. Hatchett, and lays down the following as the 

 charaderiftic properties of animal mucilsge. It is foluble in 

 cold water, infoluble in alcohol, neither coagulable by heat 

 nor generating into a jelly, precipitable by tan and the nitro- 

 muriate of tin +. I have been induced from the refults of my 

 obfervations, to form a different opinion refpeding the relation 

 of jelly and mucus, but I fliall defer the fti tement of it until 

 I have related the experiments which have led me to diflent 

 from fuch high authority. 



By agitating for a fhort time fome recent faliva in cold Mucus obtained 

 water, part of it was diflblved, and after being palfed through 

 a filter, was made the fubjed of experiment, being, as I 

 conceived, a folution of nearly pure mucus. By a careful 

 evaporation I found that the water had dilfolved -j*^ part of 

 its weight. 



* Hatchett, Phil. Tranf. 1800. 36,9 and 381. 

 t Thomfon, IV. 503. 



No 



from fali?a. 



