fibrillar substance, separated by a strip of conjunctival membrane. We will now take up the series of longitudinal sections, the study of which will demand very special attention. We shall there meet again with the organs which we have already examined in the horizontal sections; and we shall perceive that the alterations and modifications presented to us by the difference in our point of observation, bring out very important changes in the appearance of those organs. The sectional method of examination is also one of analysis. In order to reconstruct an organ in its complete form and to conceive of it in space, our mind must bring into a single focus what the sections have represented in a fragmentary manner: we must, in short, substitute synthesis for analysis. Figure 13 represents the first and exterior longitudinal section; it hardly touches the ganglion; in the front we see the starting point of the crural nerve, and also a portion of the periphery of the crural lobule. The crural nerve exhibits several roots, the most important of which occupy the ventral region. Figure 14, though very elementary, brings out many important points; we see here the crural lobule, which has increased in size and extends from the ventral to the dorsal region; a fact which has already been indicated in the horizontal sections, the crural lobule having been shown in them at all points. This lobule is almost circular in form. Along its ventral region, we perceive some of the fibres of the crural nerve which do not penetrate into the lobule; these are the ones we met with in the figures 2 and 3: they are the fibres which pass directly into the lower ventral lobule. With Section 15, we leave the lateral regions of the ganglion and come to the dorsal and ventral regions; we must notice that the crural lobule is continuous with the central fibrillar mass and has no precise limits. In Section 15 the ventral column appears, reduced in size. In the front of it we observe an incisure through which certain nerve-cells send their prolongations into the fibrillar substance.