1867.] 



Mr. Callender on the Thyroid Body. 



187 



and resembles the base of the process in either figure 6 or 7, wanting the 

 stalk-Hke continuation towards the os hyoides. The right lobe is some- 

 what irregular along its upper border ; but just where it reaches the 

 middle line there is a lozenge-shaped piece of gland, more closely con- 

 nected with the right than with the left lobe, from which latter it is sepa- 

 rated by a distinct fissure, a faintly marked line extending above for a short 

 distance between it and the right lobe. This lozenge -shaped portion ascends, 

 and is adherent to the lower notch in the middle line of the thyroid carti- 

 lage ; its extremities are pointed, and the lower one just falls short of the 

 level of the inferior margin of the lateral masses. In another foetus (fig. 

 11)*, the left lobe, three-tenths and a half of an inch in length, is irregu- 

 larly and slightly notched. The right lobe, traced towards the middle line, 

 shows scarce a sign of a middle portion ; but there is a small distinct mass 

 adhering closely to it, and this narrowing rapidly, becomes over the thy- 

 roid a slender band, and can be traced upwards until it ends by adhering 

 to the posterior inferior surface of the hyoid bone. 



The evidence obtained from these dissections goes to show that the thy- 

 roid is connected, in man, from a very early period with the upper portion 

 of the air-tube. It does not consist, at all events after the seventh week, 

 of distinct lateral masses, and the appearances it presents at that date are 

 in favour of the middle portion being of equal standing with the rest. 

 It is marked out, more or less distinctly, into three principal parts or 

 lobes, but these are united at the seventh week of foetal life and form, 

 save exceptionally, one thyroid body. 



The isthmus appears to consist of the smaller middle division uniting 

 the other two, but there may be an absence of isthmus through failure of 

 this unionf, the middle portion joining the right or left lobe, and thus 

 making one lateral portion larger than the other, a condition sometimes 

 recognized in the adult ; or a small middle lobe may remain distinct 

 (fig. 10), and this, with the various irregularities observable in the 

 lateral portions, may account for the partial and isolated outgrowths of 

 this body in various forms of goitre:]:. 



The pyramid of Lalouette may be seen in figs. 6, 7, 8, 10, and 11, 

 where it is drawn as springing from the middle, the right and the left of 

 the thyroid. It is very commonly met with in the foetus, and is clearly an 

 outlying part of the body, of which the buds seen in figs. 7 and 10 are the 

 simplest forms, and the cleft of the left lobe in fig. 6, or the distinct pro- 

 cess in fig. 8, the larger development. Just as the cornua of the thyroid 

 body are fixed by fibrous tissue to the wings of the hyoid bone, so also, as 

 would be expected, any one of these processes is equally fixed to one of 

 the adjacent cartilages, or, if prolonged upwards, to the os hyoides, as in 



* See also specimen No. 7. 



t See Sir Astley Cooper's specimens in the Museum of the College of Surgeons, 0. 38. 

 \ In the Museum of the College of Surgeons is a specimen showing enlargement of 

 the middle lobe of the thyroid, No. 1.504. 



VOL. XVT. S 



