Page:Proceedings of the Royal Society of London Vol 1.djvu/232

Rh comparatively shorter; and that they become corrugated at the tem- perature of 156° of Fahrenheit, when their tendinous and ligamentous attachments are dissolved, and their serous juices coagulated. He then proceeds to give a very minute description of the situation and arrangement of the various series which form what are called the Lateral muscles of the body. The nerves belonging to these muscles are also described; and mention is made of loose transparent vesicles about the size of a millet-seed, containing a white substance like carbonate of lime, which vesicles are found within the sheath of the nerves, at the point of their juuctions.

The rate at which fishes move through so dense a medium as water, is, our author says, very remarkable; and although this may be partly accounted for by the large proportion of muscles, and their advanta- geous application, yet the power would be inadequate to the effect if it were not suddenly exerted: this appears from the slow progress of eels, and such other fishes as, from their length and flexibility, are incapable of giving a sudden lateral stroke.

But the quickness and force of action in the muscles of fishes is counterpoised by the short duration of their power. Those accus- tomed to the diversion of angling, know how soon the strength of fishes is exhausted; for if the hooked fish is kept in constant action, it soon loses the ability to preserve its balance, and turns upon its side. This, Mr. Carlisle says, has been vulgarly attributed to drown- ing, in consequence of the mouth being closed upon the hook; but the same effects, he says, take place when the hook is fastened to the side or the tail; and he thinks that this prostration of strength may depend partly on fear, and partly on interrupted respiration; since fishes, when swimming rapidly, keep the membrane branchio- stege closed, and when nearly exhausted, act violently with their gills.

The shortness of the muscular fibres, and the multiplied ramifi- cations of the blood-vessels, are probably peculiar adaptations for the purpose of gaining velocity of action, which seems invariably con- nected with a very limited duration of it. Such examples, our author thinks, form an obvious contrast with the muscular structure of slow moving animals, and with those partial arrangements where unusual continuance of action is concomitant.

Since Mr. Carlisle's former communications respecting the arteries of slow-moving muscles, another instance has been pointed out to him by Mr. Macartney, in the muscles of tlhe feet and toes of birds, which seems to be an adaptation for the alternate rest of their limbs while sleeping.

The muscles of the human body which perform the most rapid actions, have their fibres subdivided by transverse tendons, or are arranged in a penniform direction. The semi-tendinosus and semi membranosus of the thigh are thus constructed, and the recti abdo- minis are divided into short masses by transverse tendons. All these muscles cooperate in the action of leaping.

These observations, the author thinks, tend to explain that diversity