478 Ralph H. Major. 



double injections were made by using carmine and ulti-amarine blue 

 injection masses. The carmine was hrst injected into the arter- 

 ies and continued until the capillary bed was filled ; then ultramarine 

 blue was injected into the arteries, forcing the carmine out through 

 the capillary bed and over into the veins. The ultramarine blue 

 granules fill the arteries, but fail on account of their large size to pass 

 over into the capillaries, and if we stop at the proper moment we 

 have a double injection, in which the arteries are injected blue, the 

 capillaries and veins red. Partial injections also gave some very in- 

 structive specimens. After injection the specimens were hardened 

 in alcohol or formalin, imbedded in paraffine or celloidin, cut and 

 cleared in creosote. It was also possible, by taking a small piece of 

 an injected gland, to dissect out under the binocular microscope, 

 lobules and even single follicles. This, in the case of the human thy- 

 roid, gives perhaps the most instructive specimens, as a mounted 

 specimen thick enough to contain a whole lobule, is usually too thick 

 to be studied succesfuUy under the microscope. Also a lobule or fol- 

 licle when dissected out, can be turned about and studied from va- 

 rious sides. 



The general form and shape of the human thyroid as well as its 

 gross blood-supply is described in almost any text-book of anatomy. 

 Also the variations in shape and position of the thyroid gland in 

 various animals is described in the text-books of comparative an- 

 atomy. It will be remembered that the thyroid of the cat and the 

 dog differs from that of the human in consisting of two bean-sha2:>ed 

 lobes, one on either side of the trachea, which are connected in the 

 cat by a very thin strip of an isthmus and more completely separated 

 in the dog. In these animals, too, the inferior thyroid artery is of 

 very small size and by far the greater part of the blood reaches the 

 gland through the superior thyroid artery. 



There seems to be considerable discussion as to the existence of 

 anastomoses in the human thyroid, between the superior and the 

 inferior thyroid arteries. Landstrom (19) and also Streckeisen (18) 

 show clearly by their injections that such anastomoses are present 

 upon the surface of the gland, not only between the arteries of the same 

 side, but also between the two sides. In my own injections such sur- 



