lb 
observations made in all classes of animals, and in the same 
species at different periods of age. There are some facts in 
connection with the changes occurring in disease which afford 
support to this view, which involves three positions. That 
in the nutrition of muscle the pabulum invariably becomes con- 
verted into germinal matter ; that the latter undergoes change, 
and gradually becomes contractile tissue ; and that all the con- 
tractile material of muscle was once in the state of the material 
of which the nuclei or masses of germinal matter are composed. 
It is not deposited from the blood, nor produced by the action 
of the nuclei at a distance, but it results from a change in the 
very matter of the nucleus itself. The manner in which this 
occurs has been already discussed in the paper above referred 
to (‘Archives,’ No. XIV). It was shown that the oval 
nucleus could be followed into a very fine band of contractile 
tissue or fibrilla (PI. Ill, fig. 13). We pass from the matter 
of the nucleus into very transparent imperfectly formed 
tissue in which no transverse lines are perceptible, and from 
this into fully developed contractile material in which the 
characteristic transverse markings are fully developed. 
Of the Capillaries. 
The capillaries of the papilla of the frog’s tongue are re- 
markable for their large size. In the common frog there is a 
complete vascular ring at the summit of the papilla, through 
which the bundle of nerve-fibres distributed to this part pass. 
In the Hyla the same is observed in some of the papillae, but 
the more common arrangement may be described as a half 
ring or a simple loop, bent upon one side at its upper part 
(PI. I, fig. 1). 
When the large capillaries of the papilla are distended 
with transparent Prussian-blue injection, their Avails are seen 
to be of extreme tenuity and transparency. Connected with 
the transparent tissue are numerous oval masses of germinal 
matter (nuclei), which are separated from one another by very 
short intervals. Some of these masses project slightly from 
the inner surface of the vessel into its interior, but the 
majority seem to be upon its external surface. Of an oval 
form, many of these latter gradually taper into thin fibres 
■which are continuous Avith the tissue of Avhich the vascular 
Avail is constituted. The delicate membrane constituting the 
vascular Avail exhibits longitudinal stride, which are probably 
produced in its formation, and by its external surface is con- 
nected Avith the delicate connective tissue Avhich forms, as it 
Avere, the basis-substance of the papilla, and intervenes 
