TI1YMUS GLAND. 



1101 



cation of a former opinion, that of Cowper 

 and Haller, who regarded the thymus as 

 belonging to the class of conglobate glands. 

 It appears on the whole more consistent with 

 the various facts bearing on the subject which 

 are in our possession, and yet it is by no 

 means proved, and is open to some objections. 

 In the first place, one is inclined to look sus- 

 piciously on any hypothesis, which assigns the 

 production of a material almost universally 

 diffused throughout the body to any separate 

 organ, it seems far more truth-like to regard 

 the manufacture of the plastic element 

 (fibrine), as taking place in the blood itself by 

 the agency of the white corpuscles, as Drs. 

 Addison, Williams, and Carpenter, have well 

 nigh demonstrated to be the case. If their 

 view be correct, it becomes still more impro- 

 bable that the thymic nuclei should be the 

 producers of fibrine, seeing that they are al- 

 together dissimilar in appearance and struc- 

 ture from the white granular corpuscles. 

 Moreover the early disappearance of the 

 thymus in birds, long before the demand for 

 plastic material can have materially dimi- 

 nished, makes it unlikely that in them its 

 function is the elaboration of fibrine. The 

 same observation applies to mammalia though 

 in a less degree; and, generally, I think there 

 can be little doubt that the self-forming, self- 

 sustaining blood, while supplied with an ade- 

 quate quantity of proper nourishment, is fully 

 capable of evolving within itself all that is 

 requisite for the nutrition of any part of the 

 system. 



It seems almost unwise to broach any 

 further speculations respecting this ignotiim 

 quid, especially after stating objections to the 

 views of others ; and yet while ideas are of- 

 fered as mere suggestions, to serve if they may 

 as aids to the discovery of truth, they are not 

 without utility, since none can say without 

 trial which of these " scintilla;" may kindle the 

 light of truth. From the careful investigations 

 which have been made respecting the age at 

 which the gland attains its highest develop- 

 ment, and the conditions which chiefly affect 

 its size and repletion, it certainly appears to 

 be a very exact exponent of the state of the nu- 

 trient processes generally, a delicate barome- 

 ter of nutrition, as Mr. Simon terms it. More- 

 over its anatomical constitution, as 1 have 

 insisted, seems to show that it does not truly 

 secrete, i. e. elaborate and separate some pe- 

 culiar principle from the blood, but that it is 

 a congeries of (nuclear) particles, which can 

 only be regarded as solidified liquor sanguinis, 

 and not in anywise as a true secretion, espe- 

 cially when we remember that in every such 

 fluid the nuclei of the producing cells sooner 

 or later disappear. Chemical analysis, as we 

 have seen, confirms this position ; the formula 

 expressing the nature of the contents of the 

 thymic cavities being identical with that of 

 proteine. 



Now if one of the organs which belong to 

 the class of ductless glands have for its func- 

 tion to act as a living attractive recipient or 

 reservoir for the blood en masse, may not an- 



other fulfil its destined purpose by serving as 

 a reservoir for that part of the blood which 

 ministers to nutrition, perhaps for the plastic 

 element of the liquor sanguinis in particular ? 

 When such plastic material is in superabund- 

 ance in the circulating current, a quantity of 

 it passes off, and solidifying in the thymic 

 cavities, assumes that most universal of all 

 organized forms, the form of nuclei.* When 

 there is again a demand for such material, 

 the solidified particles would again liquefy, 

 and re-enter the impoverished blood. It is 

 not difficult to understand that such a func- 

 tion may be most necessary during the pe- 

 riod when growth is most active, the sup- 

 plies of nourishment most frequent, and the 

 waste of the tissues most rapid, but that as 

 the several nutrient processes, both of the 

 assimilative and destructive kind, attain to 

 more steadiness and equilibrium, diminishing 

 somewhat in their intensity and rapidity, but 

 increasing in real strength, firmness, stability, 

 and perfection (one is obliged to use somewhat 

 metaphorical language), it may no longer be 

 requisite, and the organ will therefore undergo 

 a gradual atrophy. 



This hypothesis, which is really little else 

 than an expression of the facts above noticed, 

 has been principally suggested by the con- 

 sideration of the nature of the secretion (so 

 called) of the thymus, wherein it differs ab- 

 solutely from all other glands, in as much as 

 the nuclei constantly remain in their primitive 

 state, and are not even mingled with granular 

 matter ; while it agrees in this respect with 

 another organ of similar kind, the spleen, 

 whose parenchyma consists of similar bare 

 nuclei, which exert so far as we know no real 

 secretory action. It is however by no means 

 improbable, that, even if this guess at the use 

 of the thymus be correct, we are yet very far 

 from being fully acquainted with all the rea- 

 sons why it exists, and why in such a situa- 

 tion, and under such a form. If Mr. Goodsir's 

 account of its origin, from a portion of the 

 blastoderma, with the suprarenal capsules 

 and thyroid, be correct, it is possible that its 

 formation may be demanded by some recon- 

 dite law of development, in virtue of which 

 the extraction of one organ out of the pri- 

 mitive blastema necessitates, by a kind of 

 compensating action, that another should arise 

 in some sense complementary to it. This 

 idea, originally stated by Treviranus, has been 

 developed very ably and pleasingly by Pro- 

 fessor Paget, to whose lectures 1 refer for a 

 full exposition of it. 



MORBID ANATOMY. Not much is known, 

 and probably there is not much to be known, 

 respecting the morbid conditions of the 



* I would here direct attention' to the remarkable 

 fact, that in all glandular, and in tact in almost all, 

 organs, the nuclei are almost precisely similar in 

 size and appearance, and do not differ from each 

 other in different parts more than individual ones do 

 in the same. Does not this indicate strongly a 

 tendency of liquor sanguinis effused in conditions of 

 healthy nutrition, to assume the form of nuclei, irre- 

 spective of the situation or special endowment of the 

 part where it is effused ? 



