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In this way the central marrow of the Vertebrates divides clearly into its two chief sections, brain and spinal cord. But in these it soon passes away, the one vesicle being divided into several successive parts by transverse constrictions. In all the Craniotes, from the Cyclostoma up to man, the same parts develop from these five original cerebral vesicles, though in very different ways.
A minute cut is made in the skin, and an infinitesimal quantity of vaccine matter is inserted into the wound. Within a certain time a vesicle appears in the place of the wound, and the fluid which distends this vesicle is vaccine matter, in quantity a hundred or a thousandfold that which was originally inserted. Now what has taken place in the course of this operation?
They are egg-shaped, about an inch in diameter, and furnish the germs or ovules. These germs or ovules are very small, measuring about 1/120 of an inch in diameter. DEVELOPMENT. The ovaries develop with the growth of the female, so that finally at the period of puberty they ripen and liberate an ovum or germ vesicle, which is carried into the uterine cavity of the Fallopian tubes.
But it does please me to read the first descriptions of parts to which the names of their discoverers or those who have first described them have become so joined that not even modern science can part them; to listen to the talk of my old volume as Willis describes his circle and Fallopius his aqueduct and Varolius his bridge and Eustachius his tube and Monro his foramen, all so well known to us in the human body; it does please me to know the very words in which Winslow described the opening which bears his name, and Glisson his capsule and De Graaf his vesicle; I am not content until I know in what language Harvey announced his discovery of the circulation, and how Spigelius made the liver his perpetual memorial, and Malpighi found a monument more enduring than brass in the corpuscles of the spleen and the kidney.
We have already seen that this nucleated vesicle is itself a type of mature and independent being in the infusory animalcules, as well as the starting point of the foetal progress of every higher individual in creation, both animal and vegetable.
As the vesicles generally increase in size and number in the upper parts of a stream of lava, so would the effects of their compression increase; the yielding, moreover, of each lower vesicle must tend to disturb all the softened matter above it.
Dermoids of the rectum are reported. Duyse reports the history of a case of labor during which a rectal dermoid was expelled. The dermoid contained a cerebral vesicle, a rudimentary eye, a canine and a molar tooth, and a piece of bone. There is little doubt that many cases of fetus in fetu reported were really dermoids of the scrotum.
Few persons feel any anxiety from the impossibility of determining at what precise period in the development of the individual, from the first trace of a minute germinal vesicle, man becomes an immortal being; and there is no greater cause for anxiety because the period in the gradually ascending organic scale cannot possibly be determined.
The scar bears the shape of the original vesicle, and is slightly depressed below the surface of the surrounding skin; the surface of the scar is marked by a number of small depressions of various shapes, corresponding, I believe, with the cells in the original vesicle. 12th. Is vaccination, in hot countries, attended with feverish symptoms? and, if it is, on what day do they begin?
Attention is directed by Darwin to the more relevant fact that few persons feel any anxiety from the impossibility of determining at what precise period in the development of the individual, from the first trace of a minute germinal vesicle, man becomes an immortal being.
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