IMPROVED SCARIFICATOR. 34J 



the patient; if to obviate these inconveniences the main 

 spring be made very strong, it is then, from its confined 

 situation, exceeding liable to break; and if this does not 

 happen, another inconvenience is produced, viz. from its 

 very great strength it is scarce possible for any person to 

 cock and discharge it with (he requisite ease. 



It was therefore suggested, that, if two rows of lancets Improvement 

 could be made to move in contrary directions, these, by suggested * 

 keeping the skin equally stretched, would form clean inci- 

 sions with much less force than in the former method : The 

 scarificator A, marked No. 1, was therefore constructed, 

 and first used early in 1802 ; it is accompanied by its work- 

 ing model B; this instrument at first contained the twelve 

 long-edged spiral lancets C. 



This instrument immediately showed its theory to be Defects of this 

 good, but it had its faults; the incisions were too long when constructlon ' 

 of the necessary depth ; from the complex nature of the two 

 racks, &c, and from the confined situation to which they 

 were restricted, they could not be placed in the most fa- 

 vourable position for motion, and were therefore liable to 

 be out of order. 



These and many other objections were altered or removed These defects 

 in various ways, which at length terminated in the construe- removed > 

 tion of the instrument D, marked No. 2, also containing 

 twelve lancets, combining every advantage and improvement 

 suggested by experience and reflection. This instrument 

 admits of two main springs, but from the manner in which 

 the racks work in each other, and in their respective 

 pinions, they in effect become one, but maintain the advan- 

 tage of being made more slight, and consequently admitting 

 a greater extent of motion than a single stiff spring can 

 possibly accomplish ; beside which they are not so liable to 

 break; and should this happen to one, the instrument 

 would not be useless, for I believe that one of these springs 

 would be strong enough forall ordinary purposes, as incisions 

 are effected with much less force when the lancets diverge; 

 but combined they never have shown the least disposition to 

 stop, however deep it might be necessary to set them, or 

 strong the integuments to which they were applied ; and 

 consequently attended with greater ease to the patient. On 

 2 A 3 inspecting 



