65 
mach in several animals, along more or less only of the tube in man 
and some other mammals, and wholly absent from it in many of the 
lower Vertebrata—because this fibre has all the anatomical charac- 
ters of the muscular fibre of animal life, which no completely in- 
voluntary muscle has hitherto been found to possess*. If we are 
to judge of the office of the fibre in question from its structure, it 
must be concluded that in many Vertebrata the whole length of the 
gullet is capable of voluntary motion, in some the lower or poste- 
rior portion is not obedient to the will, while in others the motions 
of the entire gullet must be quite involuntary. 
That the muscular coat of the gullet should differ in animals of 
different orders will not appear surprising ; but it was hardly to be 
supposed that a difference in the cesophageal sheath would be found 
in some genera of the same order. Yet such is the fact in the Fere ; 
and it is probable that further research into the anatomy of this 
order will disclose more differences in their minute structure, espe- 
cially as my observations on the blood have shown that there is a 
remarkable diversity in the size of the blood-corpuscles or red par- 
ticles of some of the subdivisions of the Carnivora. 
Perhaps the extent of the muscular coat of the gullet may vary 
in the same subject at different periods of life. In young and middle- 
aged mares and geldings some of the muscular fibre of animal life’ 
may be generally traced on the gullet four or five inches from the 
stomach ; but in a gelding twenty-five years old this fibre could not 
be found on the last ten inches of the gullet ; and in an aged rabbit 
I found the striated muscular fascicles but sparingly on the last inch 
of the gullet, although in this animal generally they are most abun- 
dant in this situation. 
A summary of my inquiry concerning the extent of the voluntary 
muscular fibre on the gullet is subjoined. Some of the results 
may be modified by more facts, which are yet required to furnish 
a satisfactory view of the subject. I have had no opportunity of 
becoming acquainted with the researches of M. Ficinus and M. Va- 
lentin, referred to by Dr. Baly in his translation of Professor Miil- 
ler’s ‘ Physiology,’ vol. ii. p. 851. 
QuaDRUMANA. 
In this order, as in the human subject, the muscular fibre of 
animal life does not invest the lowest portion of the gullet. 
. 
CHEIROPTERA. 
In the pipistrelle, the sheath of the gullet, excepting 1-16th of 
an inch at the stumachic end, was formed of the muscular fibre of 
animal life. 
FER. 
Insectivora.—In the three British genera the muscular fibre of 
animal life covers the whole length of the gullet. 
* See Proc. Zool. Soc. 1839, p. 128. 
+ Ibid. Nov. 24, 1840, and May 25 and June 8, 1841 ; and Appendix to 
Gerber’s General Anatomy, p. 6-7. 
