MICROSCOPICAL TECHNIQUE, ETC. 163 
lated. For the second purpose we need not take so 
large a portion, provided we are sure of taking a typical 
part of the disease. This second part must be cut as 
thin as possible; the first part need not be so thin, 
but should certainly not be thick. A moderately-thin 
section maybe 5 m (about -smooth inch) thick; areally 
thin section is one about 3 m (smooth) ; a section over 
8 m (fjoFuth) may be called thick. 
In our opinion and experience, it is not possible to 
depend on getting really thin sections by any process 
except the paraffin; and, further, there is no process 
like the paraffin for preserving the relations of the com¬ 
ponent tissues to each other when the sections come to 
be cut. With frozen gum thin sections may be cut, 
but the sections are apt to be torn and folded in after¬ 
operations, no matter how skilfully executed. With 
celloidin really thin sections can seldom be cut; more¬ 
over, the celloidin is apt to take some of our stains, 
which cannot easily be removed from the celloidin, 
and a confused “ picture ” is produced. With paraffin 
infiltration the thinnest sections can be cut; the true 
histology is fairly well preserved; the relation of one 
tissue-element to another is preserved excellently; and 
the paraffin can be removed from the sections without 
the risk of loosening the tissue from its support, before 
the staining operations are begun. We therefore 
strongly recommend the paraffin infiltration process to 
photo-micrographers—and, for that matter, to all who 
wish to study physiology, normal or abnormal, under 
the best conditions. The paraffin process does not 
