OF MICROSCOPIC OBJECTS. 163 



but perhaps the first-named may be preferred in many 

 cases. 



Before treating of separate objects it will be well to notice 

 what M. Brunetti has said on preparing anatomical speci- 

 mens. The process consists of four stages viz., washing, 

 divesting of fat, treating with tannin, and desiccation. A 

 stream of pure water is injected through the blood-vessels 

 and secretory ducts of the part to be preserved ; the water 

 is afterwards expelled by means of alcohol. To remove the 

 fat, the vessels are in like manner injected with ether, 

 which penetrates the tissues and dissolves all the fatty 

 matters. These operations occupy about two hours, and 

 the object thus prepared may then be kept for a long time 

 in ether, if desired. A solution of tannin is next injected 

 in a similar manner, and the ether washed out by a stream 

 of pure water. The preparation is then placed in a double- 

 bottomed vessel containing boiling water a sort of bain- 

 marie in order to displace the fluid previously used by 

 dry heated air. Air compressed in a reservoir to about 

 two atmospheres is forced into the vessels and ducts 

 through heated tubes containing chloride of calcium : all 

 moisture is thus expelled and the process is completed. 

 The preparation thus treated is light, and retains 

 its volume, its normal consistence, and all its histological 

 elements. 



MUSCLE. This is what is commonly called the flesh 

 of animals. If a piece be laid upon the slide under the 

 microscope, bundles of fibres will be perceived, which with 

 needles and a little patience may be separated into portions, 

 some of these being striated, or marked with alternate spaces 

 of dark and light. Some of the non-striated or smooth class 

 of muscle, such as is found in intestines, may be prepared 

 for the microscope by immersing for a day or two in nitric 

 acid diluted with three or four parts of water, and then 

 separating with needles and mounting as soon as possible. 

 Sometimes boiling is resorted to to facilitate the separa- 

 tion, and occasions little or no alteration in the material. 

 M 2 



