152 THE AMERICAN MONTHLY [ August, 
keep well in sight the chief relations and make them true —then let the others 
follow. This point, simple as it seems, is one of the most important. A 
clear drawing which illustrates the facts is the ideal, and, when realized, is 
evidence of satisfactory work preceding it. 
Of the value of drawings of the objects of study made in this way everyone 
must be assured. It is a record of past work ready for immediate reference, 
while the best memory is but an imperfect record. It is, further, a guaran- 
tee of excellent work, for an honest student cannot make a good drawing un- 
less he has a thorough knowledge; and it thus helps him to test and com- 
plete his work before he strays off to some other study. It prevents much 
of the evil of desultory work. 
4. Written description.—I have already mentioned and described one 
written record in connection with this study, the histological record. In it 
we should have a record in black and white of the history of the section, to- 
gether with any rémarks upon the histological treatment with regard to its 
success, etc. But, besides this, the thorough student would find it to his ad- 
vantage to jot down on a slip of paper, of uniform size with his drawings, any- 
thing he may think of in connection with his section, any note on its loca- 
tion in the organ and of the organ in the body, remarks on any living condi- 
tion of the organ which could not be seen in the section or drawing, e. g., 
color in the living state, any abnormality which might be observed, any 
memoranda on reading made in connection with the study of the section, 
references to literature consulted, etc. If the habit is early formed of gather- 
ing together the results of study at the time, and shaping them as if for future 
use, a mass of valuable material will begin to accumulate which will be found 
of frequent use in subsequent studies. While this practice of review, which 
fixes the results of study, is good for any independent student of natural his- 
tory, it is indispensable in the training of students in college or similar classes. 
They should be required to state the results of their study, in the most accurate 
form they can devise, an exercise which, supplementing their drawing, 
would be a brief treatise upon the subject in hand. 
This is a well-worn theme, and one which pedagogues review frequently. 
I feel, however, that the very common neglect among students of the princi- 
ples of this section of my first chapter justifies its presence here. In treating 
of histological study, surely these words, on an important help in its pursuit, 
should find a place. 
EXPLANATION OF PLATE IV. (See page 86).—Reference letters to all the Figures. 
A. Epithelium of main collecting duct. J. Outer sheath of gland and sack. 
B. C. ‘Islands’ of Epithelium in lumen of glandal- K. Blood space. 
veolus. Lu. Lumen or cavity of alveolus. 
b. c. Blood space. N. Cell nucleus. 
bl. c. Blood corpuscle. S. Lumen of the collecting sack. 
b. m. Basement membrane. Fig. 1. Camera lucida drawing of section through gland 
c. w. Side wall of gland cells. and sack. Mag. 38 diam. 
D. Flat-celled epithelium. © Fig, 2. Camera lucida drawing of cubical celled epithe- 
Du. Duct leading from alveolar portion of gland. lium. Mag. 330diam. 
E. Lumen of gland alveolus. Fig. 3. Cainera lucida drawing of columnar epithelium. 
Ep. Flat-celled epithelium of the collecting sack. Mag. 37° diam. 
G. Lumen of gland alveolus. Fig. 4. Camera lucida drawing of flat celled epithe- 
g.m. Sheathing membrane, or capsule of gland. lium. Mag. 360 diam. 
H. Cubical-celled epithelium on the surface of the 
green gland. 
The crystallography of butter and other fats. 
By Dr. THOMAS TAYLOR, 
U. S. AGRICULTURAL DEPARTMENT, WASHINGTON, D. C. 
EXPLANATION OF PLATE I. 
Figs. 1, 2, 3, and 4 represent primary crystals of boiled butter, from milch 
cows of different breeds, under differmg conditions of feed. So to II0. 
