2y4 On Animal Fluids. 



plied with impunity to the human constitution. A ponnd 

 of blood of a glandered horse transfused into a healthful 

 horse cannot excite disease, but as much blood as can be 

 transfused from two a'andercd horses into one horse can 

 excite the disease of glanders. Sugar, alkali*, &c. may 

 exist in the blond, but not be discoverable by anv known 

 re-agent on account of the small proportion of them ex- 

 isting in the blood at any given time, as 1 humbly reason, 

 and not on account of an h\ pothetical new channel — a sort 

 of north-west passage — from the stomach to the urinary 

 bladder. In the case of waters the proportion is so minute 

 of various impregnating substances, that unless very large 

 bulks be used they must escape detection. The great mas- 

 ters have accordinulv employed such large bulks. Mar- 

 e,ra.af (Opiisailes Cliynkjues, t. ii. p. 8.) did not evaporate 

 100 drops of snow or rain water in a watch-glass capsule, 

 like some modern microscopic chemists, but he operated 

 upon 100 quart measures of snow-water, in which he was 

 able to find only 60 grains of carbonate of lime, a few grains 

 of muriate of soda, and traces of nitrous acid. I had the ad- 

 vantage of making my juvenile eflTorts to perform several 

 chenuca! exercises under that great master. Professor 

 Black. Among other precepts treasured in the tablet of 

 my memory for more than 30 years, was that of employing 

 large bulks of mineral waters; and of all other things iu 

 which there was a probability of minute proportions being 

 present. The reasons of Dr. Black for not practising ac- 

 cording to this rule in the instance of the analysis men- 

 tioned, I cannot pretend to assign ; but it seems proi)able 

 that he was in possession of only a small quantity of the 

 material. As to the magnitude of the masses of matter 

 required, it is impossible to specify them ; but it is obvious 

 that analysis must fail to develop certain substances, on 

 account of the minute proportion to other things with 

 which they are mixed not being susceptible of being made 

 evident to the senses ; and, in consequence, by a due larger 

 proportion ihcy may be rendered sensible. Hence, per- 

 haps, it is that we are ignorant of many of the properties 

 of light, calorific, eleciricity, of Infectious and contagious 

 matters, &c. 



it is aruucd against me, that •' the chemical properties 



* In Dr. RoIIo's work on Diabetes, I have related an experiment in which 

 potasli was taken in such quantity that the urine became ho impregnated 

 as to affircl a precipitate of supertartrate on dropping into it tartaric acid ; 

 at the «anio time the blood did not indicate a trace of alkali; owing, as 1 con- 

 cluded] CO the small proportion of alkali to the blood. 



whlck 



