Читать книгу The Body at Work: A Treatise on the Principles of Physiology - Alex Hill - Страница 4

NOTE ON THE FRONTISPIECE

Four photomicrographs of cells or parts of cells of brain-tissue, coloured by the chrome-silver method (cf. p. 293).

A. Cell of Purkinje from the cerebellum of a man aged 45. At the bottom of the photograph is seen the rounded cell-body, with the commencement of its axon. The summit of the cell-body bears an elaborately branched system of dendrites, spread out in the plane of the section.

B. A single basket-cell of the cortex of the cerebellum (very highly magnified). The oval cell-body gives origin to four dendritic processes which branch. Thorns are to be seen on the larger process which ascends on the right. From the same process, near its origin, springs a delicate axon which thickens as it proceeds to form a basket at the right hand lower corner of the photograph. Two other branches of the same axon, which form baskets around other Purkinje-cells, are faintly visible, although out of focus.

C. Seven or eight pyramids from the cortex of the cerebrum of a hedgehog. A little below the centre of the photograph is seen a large pyramid with a single thorny apical process which bifurcates, several basal dendrites and an axon. In the upper part of the photograph are seen the apical processes of a number of pyramids of which the bodies were not included in the section.

D. The margin of the cortex (subiculum cornu Ammonis) from the same specimen. A single row of pyramids extends across the photograph. They are remarkable for the richness of branching of their basal processes, which has earned for the cells which comprise this sheet the name of “double pyramids.”

All four sections were cut vertically to the surface.

Fig. 2.—Diagram showing the Relative Positions of the Organs

of the Chest and Abdomen.

The ribs from the first to the tenth have been cut across in the lateral line. The eleventh and twelfth ribs do not reach sufficiently far forwards to be cut. With the exception of a short segment near its junction with the ascending colon, the small intestine has been removed. The trachea is seen to divide into bronchi beneath the arch of the aorta. The right lung has three, the left two lobes. The kidneys are situate behind all the other viscera. On their upper ends rest the two suprarenal capsules. The lower edge of the right lobe of the liver follows closely the line of the ribs and costal cartilages. Below the left lobe of the liver the stomach comes to the anterior abdominal wall. The transverse colon (large intestine) comes to the anterior wall below the stomach. Below the latter the wall is in contact chiefly with coils of small intestine. The vermiform appendix rests on the posterior wall. Spleen and pancreas are not shown in the diagram.

THE BODY AT WORK