AUTHOR’S ABSTRACT OF THIS PAPER ISSUED 
BY THE BIBLIOGRAPHIC SERVICE, MARCH 17 
HISTOGENESIS OF THE HEART MUSCLE OF THE PIG 
IN RELATION TO THE APPEARANCE AND DEVEL- 
OPMENT OF THE INTERCALATED DISCS 
LUCILE WITTE 
Department of Zoology, University of Kansas 
EIGHTEEN FIGURES 
INTRODUCTION 
It is the purpose of this paper to discuss the histogenesis of 
the heart muscle of the pig with special emphasis upon the time 
of appearance and the development of the intercalated discs. It 
is a much-disputed question whether the intercalated discs are 
true cell boundaries of muscle cells or whether they are only 
peripheral, darker staining substances in the regular form of 
bands. <A further aim of this paper is, if possible, to throw 
some light on the question stated above, by tracing carefully 
the formation of the discs with regard to their probable function. 
METHODS 
In making this study, pig embryo and young pig hearts were 
used in the following series, respectively, 25 mm., 38 mm., 76 
mm., 89 mm., 95 mm., 102 mm., 115 mm., 120 mm., 140 mm., 
165 mm., 176 mm., 182 mm., 201 mm., 238 mm., 251 
mm., 277 mm., and 303 mm., and four months, five months, 
eight months, and one year. Only the ventricular muscles 
were examined. The method of technic found most satisfactory 
for demonstrating the discs clearly was that employed by Zim- 
merman! and his students Palezewska? and Werner.? The 
tissues were fixed in a solution of absolute alcohol and 25 per 
cent nitric acid and stained ‘in toto’ in Griibler’s haemalum, 
after which they were embedded according to the usual paraf- 
fin method. Sections were cut at 5 w and 8 un. 
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THE AMERICAN JOURNAL OF ANATOMY, VOL. 25, NO. 3 
