The development of the human body; a manual of human embryology . i-nally derived from the olfactory epithelium but laterseparating from it (His), and, finally, that it was composedof the prolongations of certain cells situated and, for themost part at least, remaining permanently in the olfactoryepithelium (Disse). The most recent observations on thestructure of the olfactory epithelium and nerve indicatea greater amount of probability in the last result than inthe others, and the description which follows will be basedupon the observations of His, modified in conformity withthe results obtai
The development of the human body; a manual of human embryology . i-nally derived from the olfactory epithelium but laterseparating from it (His), and, finally, that it was composedof the prolongations of certain cells situated and, for themost part at least, remaining permanently in the olfactoryepithelium (Disse). The most recent observations on thestructure of the olfactory epithelium and nerve indicatea greater amount of probability in the last result than inthe others, and the description which follows will be basedupon the observations of His, modified in conformity withthe results obtained by Disse from chick embryos. In human embryos of the fourth week the cells liningthe upper part of the olfactory pits show a distinction intoordinary epithelial and sensory cells, the latter, when fully 456 THE DEVELOPMENT OF THE HUMAN BODY. formed, being elongated cells prolonged peripherally intoa short but narrow process which reaches the surfaceof the epithelium and proximally gives rise to an axis-cylinder process which extends up toward and penetrates. Fig. 238.—Diagram Illustrating the Relations of the Fibers of the Olfactory Nerve. Ep, Epithelium of the olfactory pit; C, cribriform plate of the ethmoid; G, glomerulus of the olfactory bulb; M, mitral cell.—{Van Gehuchten.) the tip of the olfactory lobe to come into contact with thedendrites of the first central neurones of the olfactorytract (Fig. 238). These cells constitute a neuro-epitheliumand in later stages of development retain their epithelial THE ORGAN OF JACOBSON. 457 position for the most part, a few of them, however, with-drawing into the subjacent mesenchyme and becomingbipolar, their peripheral prolongations ending freelyamong the cells of the olfactory epithelium. These bi-polar cells resemble closely in form and relations the cellsof the embryonic posterior root ganglia, and thus form aninteresting transition between these and the neuroepithe-lial cells. The Organ of Jacobson.—In embryos of thre
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
