MR. E. C. BABER OR THE STRUCTURE OF THE THYROID GLAND. 
581 
IV. In tlie Tortoise a double injection of the gland was made by filling the blood¬ 
vessels from the aorta with Gerlach’s carmine mass, and after about 20 minutes 
injecting the lymphatics of the gland in situ by the method of puncture with Berlin - 
blue solution—the latter, however, did not run very well. 
In several animals also the blood-vessels only were injected with a solution of Berlin 
blue. 
Methods of Hardening. 
The method employed in by far the larger number of cases was that of placing 
portions of the fresh gland (injected or uninjected) into a mixture of equal parts of 
methylated spirit and water for a period varying from a few days to a couple of weeks 
(or longer), and afterwards into pure methylated spirit until sufficiently hard for 
cutting, the hardening being sometimes completed by immersion in absolute alcohol, 
although this is not necessary. Sections of the hardened gland were then stained 
with hsematoxylin or picrocarminate of ammonia and mounted in dammar or balsam. 
The following methods were serviceable for showing special points in the structure of 
the gland (which will be referred to subsequently). 
I. Thyroid of Sheep or Tortoise hardened in a \ to 1 per cent, solution of chromic 
acid for 17 to 25 hours and subsequently in alcohol, for showing the intercellular 
reticulum. 
II. Thy roid of Tortoise hardened in Muller’s fluid for four days, stained with 
hsematoxylin and mounted in glycerine, for showing the layer of connective tissue on 
the epithelial wall. 
The following methods gave specimens which were either inferior, showing nothing 
fresh, or else were entirely useless :—(«) Immersion in a saturated solution of picric 
acid for 18 hours, afterwards in a strong solution of gum for 18 hours, and, finally, 
in methylated spirit. This method was only tried in the Ox, in which animal, it is 
only fair to state, the results obtained by other methods were very disappointing. 
(/>) Solution of monochromate of ammonia (2-| and 5 per cent.), subsequent hardening 
in spirit, (c) Immersion for two days in a mixture of two parts of chromic-acid 
solution (f per cent.), and one part of methylated spirit, afterwards in alcohol. The 
three methods recommended by Klein (Joe. cit.) for showing intra-nuclear and intra¬ 
cellular reticulum were tried with the results mentioned below. 
The general histology of the gland is certainly best shown in specimens hardened in 
alcohol only, although the facility with which the minute structure of this organ can 
be examined varies greatly in different animals, and also probably at different times in 
the same animal (vide infra, p. 586). Boecihat (op. cit., p. 13) also found hardening- 
in alcohol the most successful method. The thyroid gland of no animal, as far as my 
experience goes, surpasses that of the Dog in the facility it presents for microscopic 
examination. 
