13 
house mice were also used, but the intestinal layers of small animals 
are too compact to enable one to clearly separate the different laminae, 
and follow the nerves with clearness and precision. 
The method pursued throughout the investigation was the rapid 
Gouel, slightly modified by changing the proportions of osmic acid 
and bichromate of potassium, as was found most suitable after repeated 
experimentation. The sections were invariably cut on the freezing 
microtome, rapid imbedding in celloidin and alcohol being found in- 
applicable, the chrome silver precipitate being almost certainly de- 
stroyed. 
In the first specimen cut, no nerves could ce found within the 
limits of the mucosa, but after a series of trials a good reduction 
was at length obtained, and the requisite degree of impregnation with 
the chrome salt being once ascertained, it was comparatively easy 
afterward to obtain moderately constant pictures; except of the plex- 
uses of AUERBACH and MEISSNER, where at no time could a perfect 
reduction be had; the best obtained being but fragmentary, and in 
no case equal to some the chloride of gold method has given me; 
therefore I have nothing to add to descriptions already given of these 
plexuses, and will therefore describe solely what I have seen within 
the limits of the muscularis mucosae and mucosa proper. 
From the ganglionic masses of the plexus of MEISSNER numerous 
fine and coarser non-medullated nerve fibres came off, that run in 
pairs, or in bundles of three or more, toward the mucous layer; to 
pass into the muscularis mucosae, or to the structures nearer the free 
surface of the organ. Many of these small bundles accompany the 
arterioles, the fibres twisting all around the vessels, at times branching 
upon them, and though occasionally becoming very delicate and split 
up upon the wall, yet they never seem to penetrate the outer sheath 
of the arteriole. 
Those that run distinct and apart from the vessels are not so 
tortuous in their course, and proceed almost vertically into the mucosa 
before branching; or they may divide sparingly before reaching that 
layer. However, from both arterial and non-arterial nerves, filaments 
go to make up a sub-plexus in the muscularis mucosae (Fig. 1), de- 
rived in the first place from the larger twigs, but ultimately from their 
division and sub-division between the bundles of muscular fibres. 
This plexus seems to be entirely free from ganglionic swellings, 
the nerves branching dichotomously without apparent regularity. The 
fine filaments of the meshwork penetrate between the muscular fibres 
in all directions, and send off secondary filaments that here and there 
