258 Kojima 



of the trachea and the lower part of the larynx, and the thyroid gland 

 liaving been exposed, a double ligature was laid between the lower end of 

 the gland and the adjacent tissue on each side. A cut having been made 

 between the ligatures, the whole gland, including the isthmus, was quickly 

 removed with the aid of fine scissors, great care being taken not to injure 

 the neighbouring nerves. After removal of the thyroid, the attached para- 

 thyroids — which in the rat are single on each side and usually external to 

 the thyroid and attached to its border — were sought for with the aid of a 

 lens and, when found, removed and replaced in the depths of the wound, 

 which was then sewn up. The operation was performed asepticall}^ ; any 

 bleeding which occurred was controlled by pressure with sterile cotton- 

 wool soaked with dilute adrenalin. The exterior of the wound was painted 

 with tincture of iodine and completely covered with collodion. 



In all, fourteen adult male rats were subjected to thyroidectomy; but of 

 these some died shortly after, and apparently as a result of, the operation. 



(b) Parathja-oidectomy. — The thyroids having been exposed and 

 the parathyroids found, the latter were snipped away with small curved 

 scissors along with a minute portion of thyroid substance. The fact of 

 their removal was determined by examination with a lens, but to ensure 

 that the removal was complete the thyroids, after the animal was killed 

 at the end of the period of observation, were cut completely in series ; in 

 no case was any trace of parathyroid found. 



Six rats were subjected to parathyroidectom}'. One of these died five 

 days after the operation ; the others were used for experiment and 

 observation. 



(c) Castration. — This operation was performed in the usual way by 

 an incision through the scrotum and ligature of each cord, the testicles 

 then being removed. 



Eight adult male rats were castrated. All rapidly recovered from 

 the operation. 



Microscopic Methods. 



At the end of the period of experiment, the animal — or group of 

 animals — having been killed with chloroform, the organs to be investigated 

 were placed at once in 10 per cent, formol. The pancreas was always 

 freed from mesentery and from the spleen, and if small, as in the case of 

 the rat, was placed as a whole in the formalin solution ; if larger, as in 

 the dog and cat, it was first cut into a number of thin pieces. After the 

 fixation had been completed by formol the portions of organs to be 

 investigated were usually embedded in parafiin and thin sections (about 

 1/ul) were cut from them. The staining methods employed were (1) 

 haematoxylin-eosin, (2) Mallory's stain (acid fuchsin, aniline blue and 

 orange G), and (3) Muir's stain (alcoholic eosin and methylene blue). 



