THE THYROID APPARATUS 6 1 



effected by means of thyroid extract, the hemiparesis, both in 

 dogs and cats, is far more pronounced than that usually seen after 

 extirpation of the cortical areas, where this is unaccompanied by 

 thyroidectomy. In one case extirpation of the cortical layer of 

 one side of the cerebellum of a cat, was followed by a distinct 

 increase in the tetanic symptoms of the same side of the body. 

 Some years ago, Lanz described a similar but " not entirely 

 conclusive result." He points out that the remarkable disturb- 

 ance of equilibrium and the staggering walk of many thyroidless 

 dogs, suggest that a portion of the cerebellum is concerned in 

 the causation of tetany. Lanz believes that his experiments point 

 to the medulla oblongata as the chief seat of tetany, but that 

 the higher centres also exercise an influence upon the contractions. 



All attempts to localize the site of tetany have not, as yet, 

 led to any satisfactory solution of the problem. Rudinger's con- 

 tention that the condition of hyperirritability arises in the ganglion 

 cells of the anterior cornua, if not in the entire peripheral neuron, 

 did not survive the test of experiment. In a later publication by 

 Falta and Rudinger, the theory is modified to this extent, that 

 the condition of hypersensibility is attributed to the sensory and 

 motor ganglion cells, more particularly those of the peripheral 

 nerves. The authors suggest that the hyperirritability after para- 

 thyroidectomy arises from the suppression of the inhibition which, 

 under normal conditions, is conveyed from the parathyroids to 

 the spinal cord. Hence, " the continued storing of fresh energy 

 in the motor ganglion cells leads eventually to an overflow of 

 irritability, and this constitutes a tetanic attack." 



This complicated hypothesis derives its sole support from 

 the fact that adrenalin glycosuria reappears in dogs from which 

 both the thyroid and the parathyroids have been removed; the 

 inference being that the parathyroids exercise an inhibitory effect 

 upon the sympathetic nerve. The theory cannot be said to have 

 stood the test of experiment, and it does not in any way add 

 to our understanding of the symptoms which follow cerebral 

 lesions and the resection of the spinal cord. These symptoms 

 point to the involvement of other and higher nerve centres in 

 the genesis of tetany, though they do not explain the manner 

 in which the intervention of the higher portions of the brain 

 takes place. The pathologico-histological findings, described by 

 MacCallum, in the central nervous system of tetanous animals, 

 which consisted in acute degenerative changes such as swelling 

 of the nuclei of the cells of the anterior cornua and chromatolysis 

 in the cortical cells, also point to the involvement of the central 

 nervous system. 



In the present imperfect state of our knowledge of tetany, 

 all that we can do is to point to the increased irritability of the 

 nervous centres and of the peripheral nerves connected with them, 

 together with the spasmophilia to which this irritability gives 



