have hitherto been detected in muscle, appear to be no less constantly renewed, no instance is known of a lost muscle having been regenerated. Still the causes which operate in effecting the decay of bone, appear also to operate in effecting that of muscle.

It must be remembered, notwithstanding, that the individual substances of bone and muscle are of different nature and different office; and I humbly conceive, that while the ductile cellular tissue effects the repair of injured muscle, it is not concerned in the repair of bone, respecting the apparent crystalline arrangement of which some ideas will be offered in considering a future subject.

The tubulated nature of cellular tissue and its elastic qualities, appear to render it sufficient for the construction of all that vascular apparatus, which obeys the muscular actions of the heart. It explains too, why air passing under the skin, may cause flatus to extend through a great surface of the body, while those partial contractions of the tube which have been alluded to, explain

also by what means it accommodates itself to the rigidity or the relaxation of particular parts, or of the system at large. Cellular tissue varies in density according to the office it is required to fill; the tube frequently bulging into the form of cells varying in their capacities. In conformity also with the nature of its office, this substance seems to contain either oily gelatinous or mucous fluid.

The natural history of cellular tissue gives also that of membranes in general, which are more or less dense according to the diameters of their fibres, and more or less supplied with lubricating fluids in proportion as their stations require it. They are named in an arbitrary way, expressive either of their arrangement, or of the different substances they are destined to defend, to construct, or to lubricate; being abundantly furnished with blood-vessels, nerves, absorbents, and glands.

CHAPTER V.

FURTHER CONSIDERATIONS OF MUSCULAR MOTIONBONE-ULTIMATE VEGETABLE FIBRE-ULTIMATE MINERAL FIBRE-COMPARATIVE PHYSIOLOGY.

THE substance contained in the ultimate tube of muscular fibre, seems like that in many forms of cellular tissue, to be adipous, since it is abstracted in an oleaginous form by heat, leaving the tube distinctly characterized; and it would not appear that the lubricating contents or qualities of the cellular tissue alone, were sufficient for that easy and undulating motion which the extreme fibres must at all times be ready to exert among themselves, in obedience to the sudden impulse of muscular exertion.

The stimulus directly communicated to the substance of individual muscles, seems strictly to be effected by those ramifications of nerve, which they so abundantly possess; and when it is considered, that these extensions of the identical sub

stance of the brain receive their impulse through an electric medium, the circumstance would appear to account for the rapidity, with which the dictates of the will are transmitted to the muscles at large.

Swammerdam thought that the force of arterial blood communicated action to the muscles, after receiving its stimulus from the nervous system. But the irritation of which the nerves are susceptible, even after death, by galvanism and other exciting media, so as to create powerful muscular contractions, favours the idea, that the exciting powers of the nerves during life, depend upon an electric property, and that the vascular system has no primordial influence upon the faculty of muscular action.

The undulating motions of the muscles, very much resemble those of water, a quality which explains itself in the opportunity their ultimate fibres naturally possess, by reason of their structure and arrangement, of moving freely in a longitudinal direction one with another, and which their own elasticity as well as that of the cellular

tissue binding them together, admits of, with the aid of that lubricating matter with which both are supplied. The quantity of space in proportion to the quantity of matter, is sufficient to allow of an approach to the undulating motion of water; bodies being more fluid in proportion as the quantity of space is greater than the quantity of matter, whereby their constituent particles are enabled to move in a corresponding ratio among each other.

Where the animal body becomes emaciated from long continued disease, the diminution of bulk is more than equal to that of the adipous substance, which fills up the spaces between the muscles, and gives regularity to the form: in other words, the waste seems deeper seated than in the common cellular integument, notwithstanding its thickness; and as a diminution of bulk cannot take place without a diminution of substance, it becomes necessary to look for that extra degree of bodily exhaustion beyond the limits of what, in vague and general language, is called the cellular substance; and the diminu