350 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Mitosis in Grafted Tissue.* — A. Pettit observed, in a thyroid and 

 parathyroid engrafted in a dog, that among the obviously degenerated 

 cells there were many instances of normal mitosis. 



Survival of Excised Cornea.f — A. Magitat calls attention to recent 

 work on the survival of leucocytes m vitro, on the recovery of motion 

 in spermatozoa after eight days, and so on. These investigations led 

 him to experiment with the cornea of the rabbit. The eye was excised, 

 sterilized, and put in blood serum at a low temperature. After 10 to 

 12 days the cornea was still almost quite translucent, and grafting 

 experiments seemed to show that it was alive. 



c. General. 



Converse Relation between Ciliary and Neuro-muscular Move- 

 ments.}— A. G. Mayer finds that the effects of the ions sodium, mag- 

 nesium, calcium, ammonium, and potassium upon neuro-muscular move- 

 ments are in each case the exact opposite of their effects upon the ciliary 

 movements of animals. (Various species of motile fungi and algas 

 react diversely to these ions, and the above statement applies only to 

 animals.) 



Ordinary ciliated epithelium, such as that covering the external 

 surface of " Trematodes " (does not the author mean Turbellariaus ?), 

 is not wholly under the control of the nervous or muscular system of 

 the animal, and the cilia continue to beat even when the muscles under- 

 lying them contract. 



The more highly specialized cilia, however, such as those of the 

 meridional combs of Ctenophores, the lobes of Veliger larvae, the peri- 

 stomial ring of trochophores, or the longitudinal band of Semper's 

 Actinian larva, cease to beat when the muscles underlying them contract, 

 and resume their rhythmic movement only when the muscles relax. 

 Thus an electrical stimulus which causes the muscles to contract stops 

 the cilia ; but if the muscles be anaesthetized with magnesium so that 

 they cannot contract, an electrical stimulus does not stop the cilia. The 

 stopping of the cilia is therefore dependent upon the contraction of the 

 muscles. It appears, then, that the stimulus which produces ciliary 

 movement tends to cause muscular relaxation, but is too weak to prevent 

 muscular movement ; but the stimulus which produces muscular con- 

 traction is of an opposite nature, and is more energetic than that required 

 to maintain ciliary movement, and completely overpowers it, stopping 

 the cilia when the muscles contract. 



Considering all things which normally affect the animal, whatever 

 stimulates the neuro-muscular system inhibits ciliary movement, and 

 whatever stimulates cilia depresses neuro-muscular activity. 



Among the cations of sea-water, sodium is the most potent inhibitor 



of ciliary activity and the most powerful neuro-muscular stimulant. On 



the other hand, magnesium is the most potent in maintaining ciliary 



movement and the most powerful inhibitor of neuro-muscular movement. 



Ammonium at first stops, and finally permits the recovery of ciliary 



* G.R. Soc. Biol. Paris, lxx. (1911) p. 2. t Tom. cit., pp. 46-8. 



t Publications Carnegie Inst. Washington, No. 132 (1910) pp. 1-25 (8 figs.) 



