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Because Anemia results from a form of malnutrition caused by the absolute inertia of the digestive function. BOVININE comes to the rescue by supplying a vitalized and perfectly compounded pabulum that calls for no chemico-vital effort whatever. Apply the crucial test-clinical use-at our expense, and convince yourself that our claims are neither extravagant nor exaggerated, but are strictly based on science. The Bovinine Company 75 West Houston Street, NEW YORK THE JOURNAL OF COMPARATIVE NEUROLOGY. THE NEUROFIBRILLAR STUCTURES IN THE GANGLIA OF THE LEECH AND CRAYFISH WITH ESPECIAL REFERENCE TO THE NEURONE THEORY. By C. W. Prentiss, Parker Fellow in Zoology, Harvard University. With Plates V and VI. A previous publication treats in detail of the fibrillar networks in the neuropil of the leech. In the present paper it is purposed to give a more general description of the fibrillar structures found in the nervous system of the leech and crayfish and to point out the relation of these structures to the neurone theory. The neurone theory, grounded upon the fundamental researches of GUDDEN, GOLGI, and His, was first formulated by WALDEYER (91) in the following words: "Das Nervensystem besteht aus zahlreichen, unter einander anatomisch wie genetisch nicht zusammenhängenden Nerveneinheiten (Neuronen)." AS WALDEYER, VERWORN, and NISSL have shown, the all-important point embraced in the neurone theory is not the anatomical independence of the nervous elements, but the assumption that the nervous system is entirely composed of cell individuals. Whether the processes of these cells are only in contact, or by growing together have become continuous, is a secondary matter. Nevertheless, on the threefold evidence of histogenesis, neuropathology, and histology, most neurologists maintain that the nervous system is composed of anatomically independent, cellular units. 1. Histogenesis. That the nerve elements develop from single neuroblasts and not from chains of cells was first asserted by His ('89, '90). His work has recently been confirmed by the excellent research of HARRISON (:01). The latter was able to show that in two cases dorsal processes from bipolar neuroblasts of the sensory ganglion broke through the bounding membrane of the nerve chord, while ventral processes from the same cells were traced to the periphery. Both His and HARRISON have proved that the axis-cylinders and dendrites of motor elements originate as processes from a single cell; they traced the axis-cylinder processes to the very point where the nerve fibers appear; but in no case did either investigator demonstrate direct connection between these processes and the embryonic nerve fibers. HARRISON states moreover that: "Die ersten motorischen Fasern sind schon vorhanden, ehe überhaupt lose Zellen in der Gegend der Austrittsstelle zu finden sind." Directly contrary to the observations of HIS and HARRISON, and in agreement with those of BALFOUR ('76) and DOHRN ('91) are the preliminary statements of BETHE (:02) as to the histogenesis of the nerve elements in the chick: (1) Before the axis-cylinder processes of the neuroblasts break through the bounding membrane of the chord, the fundaments of nerve fibers are formed as chains of cells; (2) coincident with the breaking through of the processes, many primitive fibers may be observed in the myotomes; (3) processes of the bipolar cells which form these nerve fibers in the myotomes may be traced into the chord with the same distinctness with which the processes of the neuroblasts (of His) may be traced out of it, and often the union of processes from neuroblast and primary nerve cell may be observed; (4) the primitive nerve fibers are differentiated simultaneously from an entensive chain of cells extending from the central organ to the periphery; (5) these cells increase in number only by karyokinesis; not until the 7th to 9th day of development are the neuro-fibrillae formed. BETHE Concludes from these observations that each nerve element represents a group or society of cells, rather than a single cell individual. His statements are as yet unsupported by published figures, but they agree both with the observations of other noted neurologists and with his own recent work on the regeneration of peripheral nerves. It is at least clear that as far as the evidence of histogenesis goes the neurone theory is still open to dispute. It is grounded on certain recognized facts, but these facts relate only to the early stages of development. Neither His nor HARRISON says anything as to the origin of the neurofibrillae, structures upon which the opponents of the reurone theory put much weight. 2. Neuropathology. GUDDEN ('89) was the first to demonstrate the fact that the cutting of a motor axis cylinder caused the degeneration not only of the peripheral fiber, thus isolated from its cell, but also of the cell and its dendrites. In new-born animals the entire nerve element atrophied and was resorbed, but never in any case were the pathological changes observed beyond the dendrites of the injured neurone. According to NISSL, FOREL ('86) first coupled these facts with the evidence of GOLGI's preparations and formulated the idea of the nervecell individual, to which WALDEYER later gave the name of neuThe two facts of neuropathology which have been used as arguments in support of the neurone theory are: (1) that nerve fibers separated from their ganglion cells degenerate and (2) that the phenomena of degeneration never have been observed to pass beyond the processes of the injured elements. rone. The experiments of GUDDEN show that it is not merely their isolation from their cells which causes nerve fibers to degenerate, for the cells themselves often atrophy in young animals. BETHE (98) by isolating the neuropil of a nerve center in the brain of the crab found that the nerve elements may remain actively functional for several days, proving that the nerve elements are physiologically independent of their cells. His recent experiments in neuropathology, of which he has given only a preliminary account (:02), show that peripheral nerves will degenerate some time after isolation from their nerve cells; furthermore, that in the young dog such degenerate nerve fibers will, in the course of 6 to 9 months, regenerate all the structures of a normal nerve fiber-primitive fibrillae, perifibrillar substance and Schwann's sheath. Not only are the regenerated fibers normal |