402 Dr. O'Bryen Bellingham on Irish Entozoa. 



Genus 22. Acephalocystis. 



(Derived from a, non, necjxxXr), caput, and kvotis, vesica.) 



Gen. Char. — A simple sac filled with a transparent fluid, the coats of 

 which vary in thickness and transparency. Without either head 

 or body. The young developed between the laminse of the parent 

 cyst, and thrown off either internally or externally. 



The genus Acephalocystis is not included by either Rudolphi 

 or Bremser among the Entozoa \ Prof. Owen however has shown 

 that it is entitled to a place here. The animals which it embraces, 

 usually termed Hydatids by pathologists, are amongst the lowest 

 in the scale, consisting when young merely of a simple globular 

 sac filled with a transparent fluid, which coagulates by heat ; 

 without either body or head. When this sac attains a certain 

 size the young are developed between its laminse, and the gem- 

 mules are detached sometimes from the internal surface, as in the 

 Acephalocystis endogena ; sometimes from the exterior, as in the 

 Acephalocystis exogena. These increase in size and go through 

 the same changes as the parent cyst. 



But little attention has been paid to the specific distinctions 

 between, or to the classification of, these animals. M. T. Laennec 

 described seven species, but his names have not been generally 

 adopted. 



C Acephalocystis endogena *~\ n .. c ,, v , . , 



, J r * .** ,ry, ^Cavity or abdomen, liver, kidney, 



] r v I an< ^ °t ner parts of man (Homo). 



the operation called wiring is preferred ; this consists in passing a stiff 

 wire or tube into the nostril upon the side on which the skull has 

 become thinned, and pushing it through the brain up to this point, 

 and thus emptying the cyst. This operation is sometimes, as may 

 be supposed, immediately fatal ; at others the injury to the brain ex- 

 cites acute inflammation, the animal moans piteously, and appears to 

 suffer great pain before it dies. 



* The Acephalocystis endogena, the pillbox hydatid of Hunter, is 

 not very unfrequently met with in the liver and kidney of the human 

 subject, as well as in the ovary, testis, and cavity of the abdomen, 

 constituting a particular form of disease. They usually occur in 

 considerable numbers, and may be developed in the substance of an 

 organ or upon its exterior ; in the former case they are always in- 

 closed in an adventitious cyst, formed of condensed cellular tissue. 

 They vary in size from a pin's head to that of an orange, and have 

 been seen as large as the foetal head. The gemmules are spherical 

 and very small ; after being detached they remain for some time in 

 the parent cyst ; ultimately however they increase in size, they dis- 

 tend and rupture the parent cyst, and each becomes a parent cyst in 

 its turn. 



