16 



PRACTICAL TREATISE ON 



1 



in such a position, that the light from ^e sun, or bright 

 cloud, being received upon the speculum, the rays are con- 

 centrated upon it, and it becomes brightly illuminated, and 

 is adjusted to the focus of the lens by turning the nut, d; 

 all loss of time in the screw being prevented by the 

 spring, e. The speculum, is that part of the instrument 

 which is the most important, and is 

 in general use even in the present 

 day. Lieberkuhn was also celebrated 

 B for his beautiful injections of the 

 minute tissues and organs of verte- 

 brate animals ; many specimens of 

 which are still extant. 



^ In the museum of the Royal College 

 of Surgeons of England, there is a 

 small cabinet of two drawers, con- 

 D taining twelve 



of these valua- 

 ble relics, each 

 injection being 

 A provided with 

 a separate mi- 

 croscope, of the 

 form shown by 

 fig. 12. A B 

 represents a 

 piece of brass tube, about an inch 

 long, and an inch in diameter, pro- 

 vided with a cap at each extremity, 

 the one at A carries a small double 

 convex lens of half an inch in focal 

 length, whilst the one at B carries a 

 condensing lens three-quarters of an 

 inch in diameter. 



A vertical section of one of these 

 instruments is seen at fig. 13. A 

 represents the magnifier, which is 

 lodged in a cavity, formed by the 



Fig. 13. 



Fig. 12. 



