400 PHILOSOPHICAL TRANSACTIONS. [aNNO 1708. 



nature may be. This explains very easily a common observation, hitherto very 

 difficult to physicians, about the different operation of the same medicine in 

 different forms: viz. Why the infusion of a due quantity of purging medicine 

 produces its effects sooner and more constantly, than a like quantity of the 

 same medicine in a powder; though still more constantly in a powder than a 

 bolus; and sooner and more constantly in a dry bolus, than in pills made into 

 that form with gums that do not purge; and this difference in purging shall 

 even be considerable, according to the solubility of the gums. From whence 

 it follows, that the evacuation made by such medicines, is in proportion to the 

 quantity of those medicines that happens to be dissolved, and not to the quan- 

 tity administered. Secondly, that purging by draughts is the best form, and 

 will always have the most constant effect. 



The next consideration is, that a certain quantity of any purging medicine 

 affects us after a different manner, according to the different quantity and con- 

 stitution of the blood, or its thickness; and it was shown n the solution of 

 the problem; that if its thickness were the same, the dose should always be as 

 its quantity; but the blood also differing in thickness, the doses must be aug- 

 mented on account of its thickness. This is confirmed by daily experience ; 

 where we find, that people sick with a manifest thickness of blood, as in drop- 

 sies, the jaundice, &c. take far greater doses than they did at any other time 

 when they were not sick, or ailing in that manner. 



By a further disquisition into this matter, we find that the doses must not 

 only be greater where the thickness of blood is greater; but that they must be 

 increased in a duplicate ratio of their viscidity. This is evident by the tables 

 in Cassia, viz. 9 : 8 3 ::4 : 3 3, 1 9, 134- gr. Therefore the doses are as the 

 squares of the constitutions. So likewise 9:83:: l6 : 14 3, 13-J- gr. and 

 alternandoy : 16 :: 8 3 : 14 3, 134- gr. h. e. the doses are as the squares of 

 the constitutions. The same holds true in any other constitution, besides the 

 mean; for example, in the lowest and highest 4 : 16 :: 2134- gr. 8334-. So 

 that by this means we are not only led directly to a right use of these medi- 

 cines, and are able to find the true cause why the ordinary doses produce so 

 very different effects in different constitutions ; but we also have the solution 

 of this problem, viz. " The quantity of blood in any person being given, to- 

 gether with the ordinary and extraordinary effect of a dose of a purging medi- 

 cine, the change of that person's constitution, and the nature of that change 

 may be determined.'* 



It cannot but be a great satisfaction to the mind, to find a doctrine founded 

 on a few simple experiences, leading us into the cause of many more that are 

 very complex, difficult, and obscure; which is sufficient to prove its con- 



