.84 PRESIDENTIAL ADDRESS SECTION D. 



in some vertebrates, such as men, dogs and mice, in a state of more 

 or less disharmony causing disease.* 



Though hardly parasitological, it may be mentioned that the 

 Protozoa found in soil are being examined, and their relationships 

 with bacteria and possibly with the fertility of the soil are being 

 investigated in England, America, and South Africa. 



Important work on Nematodes, their life-histories and their 

 ■effects on the growth of agricultural food-plants — such as wheat, 

 potatoes, and tomatoes — on domestic cattle and on man has been, 

 and is still, in progress. Such work is being done in South Africa . 

 and mention may be made of the important work of Dr. F. Vegli;i 

 on Haemonchus contortus, the wire-worm of sheep. 



The Rockefeller Foundation for medical research, through the 

 agency of their International Health Board, have performed mag- 

 nificent work in the treatment of patients suffering from ancylostc- 

 lriasis (hookworm disease) in many countries. 



Very interesting and useful work has been done by entomolo- 

 gists in endeavouring to find natural enemies or parasites of noxious 

 insects. 



Animal Physiology. 



Much work has been done on the ductless glands or endocrine 

 organs and the effects of their internal secretions. We may notice 

 with interest some researches on the thyroid gland in the lower 

 vertebrates, especially the Amphibia. Tadpoles fed with mam- 

 malian thyroid metamorphosed weeks before the control animals. 

 For example, Rana catesbiana, which normally takes two or three 

 seasons in its metamorphosis, only takes one month if fed on 

 thyroid. Surgical removal of the thyroid arrests metamorphosis, 

 the tadpoles remaining as larvae though their reproductive organs 

 continue to develop. The active principle of the thyroid has been 

 isolated, and is called thyroxin. It is an iodide of an indole pro- 

 pionic acid, and the activity of the gland varies directly with its 

 iodine content. It has been suggested by Swingle and supported 

 T>y TJhlenhuth that amphibian metamorphosis is due to the inter- 

 action of different environmental agencies. TJhlenhuth suggests that 

 there is a reciprocal relation between the activities of the para- 

 thyroids and thymus, in that the former absorb a tetany toxin 

 made by the latter. The inter-rela tionships of the endocrine 



* Since this was written Mrs. Helen A. Adie has published a short 

 paper in which she states that there is an intracellular stage in 

 the development of the Leishman-Donovan hody occurring in the 

 cells of the gut-wall of the bed-bug, Cimex lectularius, and similar 

 to that of Trypanosoma lewisi in the stomach-epithelium of the 

 rat-flea. It is stated that Major W. S. Patton has confirmed this 

 intracellular stage of Leishmania donovani in the bed-bug. "Indian 

 Journ. Med. Research," IX, pp. 255-260, October, 1921). Patton, 

 himself, contributes a short note, on his findings on p. 251 of the 

 same Journal, where he states that the intracellular stage of Herpe- 

 tomonas (Leishmania) donovani occurs in the mid-gut of Cimex 

 hemiptera (rotundatus) and that Leishmania tropica has a similar 

 intracellular stage in the same insect, showing that the bed-bug 

 is a true invertebrate host of these parasites. Mrs. Adie (Nov., 

 1921) has also found Leishman-Donovan bodies in the salivary 

 ^glands of Cimex rotundatus. 



