CIRCULATION OF BLOOD. 733 



the components may be separated without much difficulty, form 

 one of the most convenient objects for the demonstration of the 

 principal forms of Nerve-tissue, and especially for the connection 

 of Nerve-fibres and Granglion-cells. — For these minute inquiries, 

 however, into the ultimate distribution of the Nerve-fibres in 

 Muscles and Organs of Sense, certain special methods must be fol- 

 lowed, and very high magnifying powers must be employed. As 

 this very difficult investigation has been prosecuted by Dr. Beale 

 with more success (in the Author's opinion) than by any other 

 Anatomist, either British or Continental, and as his methods ought 

 to be carefully studied and followed by any one who either desires 

 to verify, or feels disposed to contest, his results, the Author would 

 refer to Dr. Beale's own Treatise, in which these methods and 

 results- are fully set forth, such of his Readers as desire further 

 information upon this subject.* 



574. Circulation of the Blood. — One of the most interesting 

 spectacles that the Microscopist can enjoy, is that which is fur- 

 nished by the Circulation of the Blood in the Capillary blood- 

 vessels, which distribute the fluid through the tissues it nourishes. 

 This, of course, can only be observed in such parts of Animal 

 bodies as are sufficiently thin and transparent to allow of the trans- 

 mission of light through them, without any disturbance of their 

 ordinary structure ; and the number of these is very limited. The 

 web of the Frog's foot is perhaps the most suitable for ordinary 

 purposes, more especially since this animal is to be easily obtained 

 in almost every locality ; and the following is the arrangement 

 which the Author has found most convenient for the purpose. A 

 piece of thin Cork is to be obtained, about 9 inches long and 3 

 inches wide (such pieces are prepared by Cork-cutters, as soles), 

 and a hole about 3-8ths of an inch in diameter is to be cut at about 

 the middle of its length, in such a position that, when the cork is 

 secured upon the Stage, this aperture may correspond with the 

 axis of the Microscope. The body of the Frog is then to be folded 

 in a piece of wet calico, one leg being left free, in such a manner 

 as to confine its movements, but not to press too tightly upon its 

 body ; and being then laid down near one end of the cork plate, 

 the free leg is to be extended, so that the foot can be laid over the 

 central aperture. The spreading-out of the foot over the aperture 

 is to be accomplished, either by passing pins through the edge of 

 the web into the cork beneath, or by tying the ends of the toes 

 with threads to pins stuck into the cork at a small distance from 

 the aperture ; the former method is by far the least troublesome, 

 and it may be doubted whether it is really the source of more 



* See his Treatise " How to "Work with the Microscope," 4th Ed. (1868), 

 pp. 290-304, and pp. 330-339.— The method recommended by Mr. J. Lock- 

 hart Clarke for making Transparent Sections of the Spinal Cord, will be 

 found in his ' Observations on the Structure of Nerve-Fibre ' in the 

 " Quart. Journ. of Microsc. Science," Vol. viii. (1860), p. 66. 



