391 



move her arm or hand. The rate of these vibrations was usually 

 about 80 in a minute ; but were much increased from any slight 

 cause of general irritation. 



Upon examination of the carotids, they seemed to be somewhat 

 dilated, for about half an inch in length ; but in other parts they 

 were not larger than natural. The involuntary motions, which in 

 this lady were confined to the left side, were not in any degree af- 

 fected by pressure of the carotids on that side ; but when the right 

 carotid was strongly compressed, all the vibrations were uniformly 

 stopped ; which, says the author, hardly could occur but from re- 

 moval of undue pressure of the brain, and consequent excessive irri- 

 tation. 



On the Non-existence of Sugar in the Blood of Persons labouring under 

 Diabetes Mellitus. In a Letter to Alexander Marcet, M.D. F.R.S. 

 from William Hyde Wollaston, M.D. Sec. R.S. Read January 

 24, 1811. [Phil. Trans. 1811, p. 96.] 



Dr. Marcet, having been requested by Dr. Wollaston to examine 

 whether the serous fluid, secreted in consequence of the application 

 of a blister, could be impregnated with prussiate of potash, gave to 

 a young woman five grains of this prussiate, every hour, till she had 

 taken thirteen or fourteen such doses. After the fifth dose, when her 

 urine became blue immediately by addition of sulphate of iron, a 

 blister was applied, and the serum secreted in consequence was col- 

 lected, whilst her urine still indicated the presence of the prussiate. 

 But in this serum no prussiate could be detected. 



Dr. Marcet also repeated Dr. Wollaston's experiment on serum 

 derived directly from the blood, but with this variation, that the blood 

 was drawn by cupping ; and he could not discover the presence of 

 any prussiate. 



The author observes, that in several instances in which prussiate 

 of potash had been taken by other persons, it could not be detected 

 in their urine. As some of those in whom it failed to appear were 

 taking mercury at the time, he conjectured that the difference might 

 possibly arise from that cause ; but as in two other failures no mer- 

 cury was present, he does not lay much stress on that conjecture. 



Reply of Dr. Marcet on the same Subject. 



This letter contains the details of experiments made several years 

 since. 



First. On the serum of blood, with a view to discover some easy 

 means of detecting the presence of sugar added to it. 



Secondly. Upon the blood of persons whose urine was known to 

 contain sugar, for the purpose of determining whether it was also 

 present in their blood. 



Thirdly. Upon the blood of persons secreting, by urine, other ingre- 

 dients, which had been swallowed for that purpose, in order to ascer- 



