The Microtomist's Vade-Mecum; A Handbook of the Methods of Microscopic Anatomy (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER. VII. IMBEDDING METHODS?INTBODUCTION. 124. A word on Microtomes.?It is no part of the purpose of this. work to discuss instruments, yet a word on this subject may be helpful to the student. The freezing microtome so generally employed in England, and no doubt highly useful for the pathologist, is less than any other form adapted to the wants of the zoologist. Very thin sections can be obtained by it more readily than with any other microtome, but they are of little use when obtained. The relations of the parts of the organs are deranged by the freezing and by the thawing, and the aqueous nature of the process prevents it from being readily applicable to the mounting of series of sections. The microtome of the zoologist, therefore, must be an imbedding microtome. Now there are two methods of imbedding in general use?the paraffin- method and the celloidin method. In the paraffin method the object is cut dry, with the knife set square; whilst in the celloidin method the object is usually cut wet, and in a softer and more elastic state than paraffin objects, and always with an obliquely-set knife. It so happens that the most precise and beautiful microtomes that have been constructed are designed in view of the paraffin method, and cannot be applied, or at all events are much less adapted, to work with celloidin objects. A thoroughly equipped laboratory should therefore possess two microtomes, one for paraffin work, and one for celloidin material, or other material that has to be cut in the wet way. If the anatomist cannot afford two instruments, he will perhaps do well not to choose one of those that are adapted only for paraffin, but to choose an all- round instrument, one that without being absolutely of the highest attainable precision in paraffin work will yet g...