22 
MAMMALIAN ANATOMY 
cytoplasm in delicate strands. Note the thick cell wall of 
cellulose. 
Epidermic Cells from an Onion Bulb, Showing the Arrange¬ 
ment of Cells in a Single Layer Covering a Surface. —Mount in 
water. Stain with methylene blue and study all parts and their 
relations with care. 
A Thin Section of Potato Cut by Hand with a Section Knife 
and Illustrating the Arrangement of Cells in a Mass. —Mount in 
water. Note large size of cells, large amount of stored starch 
granules within the cell. These are brought out well by staining 
with iodine. They usually obscure the nucleus. 
B. HISTOLOGICAL SECTIONS, A METHOD OF PRE¬ 
PARING MATERIAL FOR MICROSCOPIC STUDY. 
Remove from a recently killed animal as soon as possible after 
death, small pieces of the desired tissues 1 and prepare them for 
sectioning, by the following method: 
Killing and Fixing. 2 —Place the fresh material in pieces not 
larger than a centimeter in the greatest dimension, in a consider¬ 
able quantity of the following fixing fluid for from four to sixteen 
hours according to size: 
Bouin’s Fixative. 
Parts 
Picric acid, saturate aqueous solution.,. 75 
Formaline (40% formaldehyde)... 25 
Glacial acetic acid. 5 
1 It is recommended that at this time each student begin the preparation of a 
piece of material mainly for later sectioning in connection with the study of various 
tissues and organs. Young mammals (kittens or rabbits for example) afford excel¬ 
lent material. It is also recommended that Necturus or some other amphibian be 
used, as the large size and primitive relationships of its cells render it excellent 
material for the beginning student. The following tissues and organs will prove of 
use in later work in the course: From Necturus, cartilage, voluntary muscle, intes¬ 
tine, liver; from some mammal, costal cartilage, voluntary muscle, intestine, liver, 
salivary gland, ovary, testis, artery, vein. It is possible also to obtain satisfactory 
results by making transverse sections through the trunk region of a half grown 
salamander larva, since these sections furnish excellent material for the review of the 
general plan of the vertebrate body, while at the same time affording an opportunity' 
for the examination of a variety of tissues and organs. 
2 The length of time which material should be left in any given fixative, and the 
subsequent treatment after fixation, are matters which vary with the nature of the 
fixative itself. Directions concerning these matters should therefore always be 
carefully heeded and faithfully followed. 
