1815.] Intellectual Functions of Man and Animals. 119 
the same fibrils of the same nerve; that consequently all nerves, 
having at once sensation and volition, divide into two series of 
fibrils on joining the spinal marrow, namely, an anterior series and 
a posterior one; that the anterior series is, in form and structure, 
totally different from the posterior; and that the spinal marrow, 
divided as it is by fissures and by cineritious matter, does really 
form four columns which are joined by these series, viz. the anterior 
columns, by the anterior fasciculi, and the posterior columns, by 
the posterior fasciculi. 
In reply to my statement, that the anterior columns join the 
cerebrum, and the posterior the cerebellum, Dr. Leach says, “ Gall 
and Spurzheim have shown that the brain and cerebellum cannot 
be considered. as the continuation of the spinal marrow, any more 
than the spinal marrow can that of the brain and cerebellum.” 
This reply the Doctor no doubt thinks decisive; and as I have 
shown that he has rather too hastily, and without reason, called my 
anatomical and physiological statement inaccurate, I must now, 
inquire into his. ‘The argument, then, which he here adduces, 
from whatever source derived, is a bad one, because it proves a 
great deal too much, as the following observation will show.— 
Various parts, then, of the body, have been generated separately in 
the uterus or ovaria, as hair, teeth, limbs, &c. Now, in the case 
of the lower part of the body or the lower extremity being generated 
alone or detached from the superior parts, the generated parts 
would contain vessels as well as nerves—namely, an aorta and vena 
cava, or a femoral artery and yeia. But, from the Doctor’s argu- 
ment, it would follow that, because in this case the lower parts of 
these vessels were produced separately from the upper, therefore, in 
the natural state, these parts are not continuations of each other! 
and that the aorta and femoral artery are not descending, and the 
vena cava and femoral vein ascending!* Such, then, are the 
precise and “ accurate ” arguments employed by Dr. Leach to 
prove that the anterior colamns and their nerves do not join the 
cerebrum, and the posterior the cerebellum. 
In reply to my statement, that the anterior of the nervous 
fasciculi which join the spinal marrow are not nerves of sensation, 
nor the posterior nerves of volition, Dr. Leach, instead of provin 
my inaccuracy, places upon record a most astonishing specimen of his 
own !—Dr. Leach says, “ The two roots of nerves of each half of 
the spinal marrow, namely, the anterior and posterior, ,go to dif- 
ferent parts of the body :—the muscles and skin of the back receive 
their nerves from the posterior roots, whilst the museles and skin of 
the abdomen receive theirs from the anterior roots, and yet the fore 
and back parts of the body have sensation and voluntary motion,” 
Now certainly if this were but true, my doctrine would be not 
* This argument is not limited to the separate production of one part of the 
body, as the trunk, or the lower extremity; but obviously applies to any part 
we may ever have been separately produced, and even to all degrees of muti- 
ation, 
