220 PHILOSOPHICAL TRANSACTIONS. [aNNO 1758. 



justly intended to point out the quantity of error that will happen in a large ex- 

 tent. For instance: between latitudes 10° and 6o° n. and containing HO" dif- 

 ference of longitude, Mr. Murdoch computes the distance at 5594 miles; which, 

 on the arc of a great circle, is found to be 5477, or by other methods 5462: so 

 that the difference is only 117, or at most 132 miles in so great an extent, and 

 to a high latitude; and the higher the latitude the greater the error is like to be, 

 where ever middle latitude is concerned. His courses also agree very nearly with 

 computations made from the tables of meridional parts. However, this method 

 does not appear so simple, easy, and concise, in the practice of navigation, as 

 Mr. Wright's construction, especially in determining the bearings or courses 

 from place to place: nor will it admit of a zone containing both north and south 

 latitude. 



LXXV. On the Remarkable Effects of Blisters in Lessening the Quickness of 

 the Pulse in Cougfis, attended with Infarction of the Lungs and Fever. By 

 Rob. Whytt, M. D., F. R.S. p. 569. 



One of the most natural effects of blistering plasters, when applied to the 

 human body, is to quicken the pulse, and increase the force of the circulation. 

 This effect they produce, not only by means of the pain and inflammation they 

 raise in the parts to which they are applied, but also because the finer particles 

 of the cantharides, which enter the blood, render it more apt to stimulate the 

 heart and vascular system. 



The apprehension, that blisters must in every case accelerate the motion of the 

 blood, seems to have been the reason, why some eminent physicians have been 

 unwilling to use them in feverish and inflammatory disorders till after the force 

 of the disease was a good deal abated, and the pulse beginning to sink. How- 

 ever, an attentive observation of the effects which follow the application of blisters 

 in those diseases, will show, that instead of increasing, they often remarkably 

 lessen the frequency of the pulse. This Dr. W. had occasion formerly to take 

 notice of, in his Physiological Essays, p. 69, and now evinces more fully by the 

 following cases. 



1. A widow lady, aged about 50, was seized (Dec. 1755) with a bad cough, 

 oppression about the stomach and breast, and a pain in her right side, though 

 not very acute. ' Her pulse being quick, and skin hot, some blood was taken 

 away, which was a good deal sizy: attenuating and expectorating medicines were 

 also prescribed. Bui as her complaints did not yield to these remedies. Dr. W. 

 was called on Dec. 26, after she had been ill about 10 days, at which time her 

 pulse beat from 96 to 100 times in a minute, but was not fuller than natural. 

 He ordered her to lose 7 or 8 oz. more of blood, which, like the former, was 

 8izy ; and next day, finding no abatement of her complaints, he advised a blistgr 



