CELL CHANGES IN THE CENTRAL NERVOUS SYSTEM UNDER VARIOUS NATURAL AND EXPERIMENTAL CONDITIONS. SECOND PAPER: CRETINISM IN SHEEP AND GOATS

Abstract

1. The brains and cervical cords of seven typical cretin lambs, two typical cretin kids, and one atypical cretin sheep were examined histologically from Nissl preparations for nerve‐cell changes. These tissues were properly controlled by tissues from animals of the same age and sex. In four cases—three cretin lambs and one normal—Macallum's microchemical iron reaction was employed.2. In each of the nine typical cretins definite chromatolysis of these elements were found. Sufficiently characteristic stages were represented to warrant a progressive course in the development of the process.3. The reaction is an affection of the chromatin apparatus, both nuclear and extranuclear, and is characterised by an initial increase followed by a diminution of this substance. This may lead to complete degeneration of the cell.4. The chromatin of the nucleus and nucleolus is less affected than the Nissl substance, and, except for the diffuse substance infiltrating from the cytoplasm, may appear quite normal when the extranuclear chromatin has been reduced to a very fine state. The nucleoli sooner or later, however, become swollen and lose a large part of their characteristically staining chromatin. In iron preparations these appear mottled.5. Identical stages of the chromatolytic process were demonstrated by the two methods employed. Unlike the toluidin‐blue stain, however, the hwematoxylin iron reaction brings out the oxyphilic as well as the basiphilic iron‐containing chromatin. By this method certain accessory bodies of the nucleus are shown. There is first an increase in the amount of iron‐reacting material in the nucleus, after which it begins to diminish, and may reach a point below that of the normal level.6. There is an initial decrease in the size of the cells, which is followed by a gradual swelling. Vacuolisation of the cytoplasm is frequently seen. The nucleus is affected to a less extent than the cytoplasm. Vacuolisation of the former was not observed.7. These alterations are not sufficiently characteristic to support the theory of a specific reaction, and are not in a true sense diametrically opposite in their course to those associated with parathyroid tetany, where excitation rather than depression is the prominent symptom.8. The changes are believed to be due to a state of depressed metabolism resulting from the loss of the thyroid principle, and are sufficiently advanced and extensive to account, in part at least, for the abnormal behaviour of the animals involved.The writer wishes to express his deepest appreciation to Dr S. A. Goldberg, of the Department of Pathology and Bacteriology, New York State Veterinary College, Cornell University, who conducted the post‐mortem examinations for the cases described above.The cost of this investigation has been defrayed, in part, by a grant from the Heckscher Research Foundation of Cornell University.