Section of Medical Science. 505 



tures before making its escape through them. Dr. Houston agrees 

 in opinion with those who consider that the function of imbibition is 

 carried on by the whole surface of the little animal. From the ex- 

 amination of the specimens of hydatids which existed in great number 

 and variety in this case, the author has been enabled to describe and 

 delineate the different stages of the process of degeneration, to which 

 lie considers all such animals are by their nature subjected ; and has 

 arrived at conclusions as to the seat of these degenerations different 

 from those advanced by other authors. He considers, That the term 

 allotted for the existence of each individual hydatid having expired, 

 the little animal dies, and in the dead state comes to act as a foreign 

 body on the cyst which contained it ; — That the cyst, thus irritated, 

 falls into a state of inflammation, the effects of which are traceable 

 through a variety of stages, to the almost total disappearance of both 

 cyst and hydatid. The cyst first becomes thickened ; lymph is 

 thrown out on its internal surface, giving it a roughened granular 

 appearance. The hydatid becomes opake, and its fluid contents 

 muddy. An adhesion, probably of a glutinous or mechanical nature, 

 is established between the lymph and the exterior surface of the hy- 

 datid. The fluid of the hydatid is then absorbed, and its empty 

 bag squeezed up in the centre of the solidified tumour. At a period 

 somewhat later all traces of the hydatid disappear, and the remaining 

 mass consists of nothing but the altered cyst, filled with lymph and 

 some curdy matter. The tumour diminishes in bulk, it becomes of 

 a cheesy consistence, and finally is converted into a small solid 

 nucleus of earthy matter, devoid, as it would appear, of any irritating 

 properties. 



Dr. Houston differs from other writers in referring the whole of 

 the morbid changes to the cyst, and not to the contained hydatid, 

 which he says is absorbed in the progress of the phenomena conse- 

 quent upon its death. He does not concur with those who are of 

 opinion that malignant and tubercular diseases are of the nature of 

 parasitical animals. No facts have hitherto been advanced sufficient 

 to establish the position that any such diseases are, either at their 

 commencement or at any subsequent period of their progress, of 

 such a character. No animal has ever been seen of any definite 

 shape in connexion with them ; and where the powers of the mi- 

 croscope can be brought with such effect in aid of investigations of 

 this nature, why, it may be asked, if such pestiferous animals exist, 

 have they not ere this been demonstrated ? The fact is, that all the 

 circumstances connected with the growth and decay of such para- 

 sites as our senses can take cognisance of tend to a conclusion of an 

 opposite nature, viz, that these animals have their periods of ex- 

 istence as living beings, and having passed from this state, instead 

 of polluting the whole frame, or running into extensive diseases, dis- 

 appear, and leave little or no injurious effects behind them, unless 

 what may have arisen from their mechanical interference with the 

 functions of some vital organ. 



The author exhibited numerous preparations and drawings illus- 

 trative of the facts advanced in the paper. 



Third Series. Vol. 7. No. 42. Dec. 1835. 3 T 



