OF THE THYROID GLAND OF THE DOG. 
559 
I. The Lymphatics. 
Methods. — The methods of investigation adopted were the following, viz. : — 
1. Injection with Berlin blue. — The thyroid gland of a freshly killed dog was injected 
in situ "with a solution of Berlin blue, by the method of puncture with a subcutaneous 
syringe. When the gland was sufficiently injected (the naked eye appearances it then 
presented are described below), it was removed and hardened, either 
a. In methylated spirit only, or 
b. First in Muller’s fluid, and then in methylated spirit. 
When sufficiently hard, portions were embedded and stained and mounted in balsam 
in the usual way. 
2. Injection with Nitrate of Silver. — Fresh thyroid gland of the dog was injected in a 
similar manner with ■§• per cent, solution of nitrate of silver in water. The gland was 
then removed and hardened in alcohol, and portions of it were treated as before. 
Throughout this research the thyroid glands examined were those of adult dogs only. 
Characters and Distribution. — The lymphatics of the thyroid gland, when examined 
by the above methods, presented the following characters. 
1. Macroscopic Appearances. — The thyroid gland in the dog, as is well known, consists 
of two separate portions, situate on either side of the trachea and in front of the 
vertebral column. On inserting the nozzle of a hypodermic syringe into one of 
these glands, and injecting Berlin blue solution, the following appearances presented 
themselves : — 
The whole gland swelled up, and a fine network of injected vessels appeared on the 
surface of the organ, which could be distinctly seen with a hand-lens. At the same 
time lymphatic vessels became injected running from the gland, and these were distri- 
buted in the following manner : — Several branches came off from the lower and inner 
extremity of the gland. These soon joined to form a single vessel, which, running in a 
direction obliquely downwards and inwards in front of the trachea, entered a small 
lymphatic gland situate in the median line over about the sixteenth ring of the trachea. 
The vessels emerging from the upper part of the thyroid gland, which were larger and 
more numerous than the preceding, formed a plexus immediately above it ; and from 
this there came off two principal branches, the one running upwards and inwards 
over the front of the windpipe, the other taking a course outwards and upwards and 
terminating in a large lymphatic gland situate under the upper part of the sterno-mastoid. 
This gland became partly injected with the Berlin blue. In size it nearly equalled the 
thyroid gland itself. 
On examining with a hand-lens the surface of a thyroid gland that had been 
injected in a similar manner with nitrate- of-silver solution, a fine network of lymphatics 
was also seen, resembling somewhat in shape and distribution those to be afterwards 
described in the interior of the organ (Plate 47. fig. 3). 
2. Microscopic Appearances. — Before describing these it will be necessary to say a 
few words with regard to the general structure of the thyroid gland of the dog, as I 
4 H 2 
