790 



CYST. 



become irritated and inflamed, and these tunics, 

 at first characterised by so much tenuity, may, 

 by the pure and simple effect of their rapid 

 development, or as a consequence of their 

 relation with very moveable organs, or by the 

 effect of accident, to which they are exposed, 

 become susceptible of almost unlimited trans- 

 formation. 



We believe, therefore, that ail the varieties 

 composing this class owe their existence to 

 irritation ; in the synovial the irritation is spe- 

 cific and caused by pressure, in the serous, 

 we believe it to be of another kind, in many 

 of them it is similar to that which presides 

 over the development of hydatids: the only 

 difference between certain of them, those, for 

 instance, which are so nearly isolated, having 

 merely a vascular communication, and an 

 hydatid, is perhaps simply, that their existence 

 has not been sufficiently prolonged to permit 

 with safety the rupture of this umbilical cord, 

 if I may so term it, by which they are con- 

 nected to the surrounding tissues ? We must 

 now endeavour to explain the circumstances 

 under which these cysts are developed. 



The experiments and observations of Cru- 

 veilhier shew, in the most convincing manner, 

 that humidity, abundance, and the bad or ve- 

 getable quality of the nourishment of an 

 animal, are unequivocal means of producing 

 acephalocysts. If by the concurrence of these 

 circumstances acephalocysts may be produced, 

 it must be evident that by the agency of the 

 same causes a modification of existing tissues, 

 irritation, in fact, of a specific kind, has been 

 excited by which a state favourable to their 

 development has been produced. Admitting 

 then that by such means a particular kind of 

 irritation may be set up in certain tissues, we 

 must go further; that irritation must be suf- 

 ficient to cause the exhalation of a particle of 

 lymph, that lymph, as in the case of a pseudo- 

 membrane, becomes organised, acquires step 

 by step an individual existence, it will be the 

 minimum of organisation and independent 

 vitality, but still, when its separation is achieved, 

 it will be a living being. Supposing this idea 

 to be correct, it may follow that a variety of 

 modifications of such products, more or less 

 independent, may be in a similar manner pro- 

 duced. 



It is certainly difficult to reconcile the mind 

 to the idea that the process of irritation or of 

 inflammation can, under any circumstance, 

 excite the development of an animal possess- 

 ing to a certain extent an independent ex- 

 istence, but this is not more difficult than to 

 conceive that molecules of a plastic living 

 substance may form organic membranes, and 

 ,yet this is demonstrable. 



This has been clearly shewn in the article 

 ADHESION; in fact, the more we study the 

 phenomena of organisation, the more we are 

 impelled to admit a proper vitality in certain 

 products of living bodies. The analogy which 

 exists between false membranes and hydatid 

 sacs appears to be especially calculated to 

 elucidate this subject. But whilst the false 

 membrane remains in vital communication with 

 the individual, the acephalocystic false mem- 



brane is detached and enjoys an independent 

 life ; the false membrane acquires a vitality 

 rivalling that of normal tissues. 



We believe, therefore, that a cyst may be 

 developed, which, as far as general appearances 

 are concerned, shall be analogous to the ace- 

 phalocysts, wanting, however, the one great 

 attribute, independent existence, and having 

 a vascular communication with the tissue upon 

 which it is developed : are not those cysts 

 which are often seen upon the cortical sub- 

 stance of the kidney, and upon other organs; 

 of this class or character ? 



Dr. Hodgkin* has inferred that those cysts 

 which are so often found on the surface of the 

 kidneys owe their existence to the obstruction 

 of an excretory canal; others have believed 

 that this fact was demonstrated, because it was 

 said that their contents had the odour of urine. 

 Without denying this position, I may state 

 that the smell of serum and that of limpid 

 urine are not very dissimilar. If they were a 

 consequence of the obstruction of an urinary 

 duct, it is evident, from the size they some- 

 times attain, that secretion has proceeded after 

 the obstruction has been developed ; why then 

 does it not go further ? why do they not attain 

 considerable magnitude ? 



In the earlier periods of their existence the 

 organisation of these bodies is simple, but in 

 their progress they may experience many mo- 

 difications. Their internal and external sur- 

 faces are essentially different; the internal is 

 usually smooth and polished like serous mem- 

 branes ; sometimes it is soft, flocculent, and 

 easily detached : the external is in contact with 

 cellular tissue, and partakes more or less of its 

 character, but frequently it acquires a density 

 which distinctly separates it from the surround- 

 ing tissue. There is scarcely any form of trans- 

 formation which may not occur in these organs. 

 The internal surface occasionally acquires a 

 very complicated organisation ; it may be co- 

 vered with hair proceeding from follicles de- 

 veloped in its parietes, and it may present 

 other anomalies. The external surface may 

 acquire a very considerable density, and may 

 present something like a fibrous appearance, 

 but upon further investigation we find that it 

 does not possess any fibre, neither does its 

 texture offer any linear or radiated arrange- 

 ment. When once organised, the tunic which 

 constitutes the cyst enjoys all the attributes 

 of living tissues, and is susceptible of similar 

 morbid modifications. It may become in- 

 flamed, it may degenerate into a cartilaginous 

 state, may become incrusted with phosphate 

 of lime, converted into erectile tissue, may 

 become scirrhous, and so on ; and the ex- 

 halation or secretion may be so changed that 

 cysts of similar origin may contain the most 

 dissimilar products. 



BIBLIOGRAPHY. Cruveilhier, Essai sur 1'Anat. 

 Path. t. i. p. 202 & seq. Gendrin, Hist. Anat. 

 des Inflam. t. ii. p. 531. Begin, Diet, de Med. et 

 Chir. Path. art. Kyste. 



(B. Phillips.) 



* Med. Chir, Transact, vol. xv. part 2. p. 270. 



