Page:Popular Science Monthly Volume 19.djvu/127

Rh layers thick before the formation of the ridges, and become single again over these. . . . By the intersection of the ridges, pits are left, which are the gland-pouches." The "ovoid" cells are first specalizedspecialized [sic] and later the central cells, the latter alone being concerned in the formation of pepsin.

The third article is by Professor Martin and Dr. W. D. Booker. Its subject is "The Influence of Stimulation of the Mid-Brain upon the Respiratory Rhythm of the Mammal." Having found that chemical stimulation of the mid-brain of the frog caused accelerated or tetanic inspiratory and impeded expiratory movements, experiments were made on rabbits to see if the same phenomena were exhibited by mammals. By an ingenious arrangement the animal was made to breathe into a jar, the aperture of which was covered by an elastic membrane, and through a connecting lever was made to record, on a revolving cylinder, all the respiratory movements. The stimulus applied was by means of electrodes, connected with a secondary coil of a Du Bois induction apparatus. The current from a single carbon-bichromate cell was sent through the primary coil.

Reference must be made to this memoir for further details regarding the experimental methods employed. The general results are summed up as follows: "There lies deep in the mid-brain of the rabbit, beneath the posterior corpora quadrigemina and close to the iter, a respiration regulating center, similar to that in the corpora bigemina of the frog: electrical stimulation of this center causes accelerated inspirations finally passing into tetanic fixation of the chest in an inspiratory condition, and correspondingly diminishes or altogether inhibits expiration."

The paper of Dr. I. Edmondson Atkinson, on the botanical relations of Tricophyton tonsurans, details some very careful experiments in cell-culture made in order to determine whether excessive polymorphism existed among these lower fungi.

Dr. W. K. Brooks closes Part I with a memoir entitled "Preliminary Observations upon the Development of the Marine Prosobranchiate Gasteropods." For material the author studied two common marine snails from the first segmentation of the egg to a stage when it emerges with its full class characters. Among other things he shows that, while there is no stage that can be considered as a specialized gastrula, there are presented at different periods of its development all the phases in the formation of a gastrula; and also that, while the gastrula stage has disappeared, the gastrula form persists.

Part II commences with a memoir by Professor Martin and Edward M. Hartwell, on the respiratory function of the internal intercostal muscles. The authors show how conflicting are the opinions regarding the particular mechanical work done by these muscles; and how impracticable it is to decide by a simple mechanical study as to whether these muscles are rib-elevators or rib-depressors. Dogs and cats were used in their experiments, which show that the muscles in question are expiratory in their function throughout their whole extent.

The next paper, by Isaac Ott, M. D., entitled "Observations on the Physiology of the Spinal Cord," is an account of the author's investigations of the secretory functions, vaso-dilator centers, rhythmical functions, genito-urinary functions, and path of secretory and inhibitory fibers of the cord.

On the "Effect of Two Succeeding Stimuli upon Muscular Contraction," by Henry Sewell, Esq., is a paper which affords an excellent example of how minute and exact experiments should be conducted. Among other interesting facts it is shown that a "given maximal stimulus stirs up the untired muscle to a more powerful contraction when it has been preceded by the excitement ordinarily producing contraction."

In the "So-called Heat Dyspnœa," by Christian Sihler, M. D., is an attempt to get at the causes of the increased respirations in a dog, when it is subjected to a temperature warmer than its own body. Finding previous experiments inconclusive, the author not only repeats those of Goldstein, but details a number of new ones. His conclusions are: 1. That Goldstein's experiment with the tube is inconclusive; 2. The increased respiration following exposure of the animal is due to two causes, skin stimulation and warmed blood; 3. Of these, skin stimulation is the more powerful; 4. Apnœa can be produced in heated animals,