322 On the Experimental Production of Congenital Goitre. 



Fig. 6. — Another group of scleroblasts with associated colloscleres and vesicles ; under 



the same conditions as fig. 5. x 480. 

 Fig. 7. — A group of four scleroblasts lying undisturbed in the mesogloea and each 



showing a " secretion-knob. Stained with paracarmine and mounted in Canada 



balsam, x 480. 



Fig. 8. — Two scleroblasts with associated colloscleres and vesicles, lying undisturbed in 



the mesogloea with portions of three megascleres. Stained with paracarmine and 



mounted in Canada balsam, x 480. 

 Fig. 9. — A single scleroblast with associated vesicle and collosclere probably secreted by 



itself, lying undisturbed in the mesoglcea. Stained with paracarmine and mounted 



in Canada balsam, x 480. 

 Fig. 10. — Another scleroblast, isolated by teasing, with its associated vesicle and 



collosclere. Stained with paracarmine and mounted in Canada balsam, x 480. 

 Fig. 11. — A vesicle, with contained collosclere, partially torn away from a scleroblast by 



teasing. Stained with paracarmine and mounted in Canada balsam, x 480. 

 Figs. 12-16. — Five scleroblasts, showing stages in the growth of the secretion-knob^ 



From teased preparations stained with paracarmine and mounted in Canada balsam- 



x480. 



anation of Lettering. — col., collosclere ; meg., megasclere ; mes., mesoglcea ; nu. r 

 nucleus ; scl., scleroblast ; s.k., secretion-knob ; ves., vesicle containing collosclere. 



On the Experimental Production of Congenital Goitre. 



By Robert McCarrison, M.D., D Sc., F.RC.P. (lately on Special Duty 

 for the Study of Goitre and Cretinism in India). 



(Communicated by Sir Victor Horsley, F.R.S. Eeceived March 18, 1916.) 



[Plate 12.] 



The experiment herein described was undertaken at the Central Eesearch 

 Institute, Kasauli, India. It commenced on September 6, 1913, and. 

 terminated, owing to my recall to military duty for active service, on 

 December 24, 191-1. Having been on service for the past 18 months I have- 

 not hitherto had an opportunity to report it. 



Object of the Experiment. 



Its object was to determine the cause of congenital goitre and the- 

 conditions under which it developed in large animals, and to confirm and 

 amplify the results I had obtained by previous experimentation on white rats. 



It was consequently designed so as to subject the foetuses of primiparae to- 



