704 APPENDIX. 



injected (say a sheep's kidney, which is very difficult to inject in 

 any other way, and forms an excellent criterion of success), and 

 fix his pipe in the artery, leaving the vein open. Having given 

 his material a good shake, let him pour it into a cup, and fill the 

 syringe. Now inject with a slow, gradual, and moderate pressure. 

 At first, the matter will return by the vein, colored, hut in a few 

 moments this will cease, and nothing will appear except the clear 

 ether, which will distil freely from the patulous vein. This must 

 he watched, and when it ceases, the injection is complete. The 

 kidney is now to be placed in warm water of 120 Fahrenheit, 

 for a quarter of an hour, to drive off the ether, when it may be 

 sliced and dried, or preserved in alcohol, Goadby's solution, or 

 any other antiseptic fluid. For glands, as the kidney, liver, &c., 

 it is better to dry and mount the sections in Canada balsam, but 

 for membranous preparations, stomach, intestine, &c., the plan 

 of mounting in a cell filled with antiseptic solution is preferable." 



MICROSCOPES QF AMERICAN MANUFACTURE. 



Microscopes of great excellence are manufactured in this 

 country. These, from their comparative cheapness, and the 

 facility with which they can be procured, offer inducements to 

 students and others to procure them at home, and thus save time 

 to themselves, at the same time that they stimulate the manufac- 

 turers to make increased efforts to attain even greater excellence. 

 A brief description of some of the best will enable the reader to 

 form some comparative estimate of their value. 



Mr. CHARLES A. SPENCER, of Canastota, New York, has manu- 

 factured a microscope of great excellence, the objectives of which 

 will bear comparison with the best of foreign construction. His 

 common angle of aperture for inch objectives is 135 ; for J 

 inch, 170, and for T ' z and J ff inch, 176. This is believed to be 

 the largest angle ever given to an object-glass, and for sharpness 

 of definition and power of penetration, they are unexcelled by 

 any of foreign make. 



" To Mr. Spencer is due the credit of having first resolved, with 

 lenses of his own construction, the fine markings on the Navicula 

 Spencerii and Grammatophora Subtilissima : these minute shells 

 have since been adopted by microscopists as test-objects for the 

 highest powers. The Navicula Spencerii, will exhibit one set of 

 lines with Mr. Spencer's Jth-inch object-glass : both sets with 

 the Jth-inch. The Grammatophora Subtilissima is a good test 

 for a j^th or y^th. 



Of several microscopes made by Mr. Spencer, two or three 

 only will be here noticed. His first-class or best instrument is 

 mounted on trunnions, and embraces all the acknowledged im- 

 provements, in form and stage, whereby the greatest steadiness 

 and freedom from tremor are secured. The price of this instru- 



