Keber on the Porosity of Bodies. 287 



is not free from error. " I believe, therefore/' says H. Meckel, 

 " that that alone ought to be regarded as the true egg which 

 exists in Man, Mammalia, Naked Amphibia and Osseous 

 Fishes ; and that in the remaining Vertebrata the ovum consists 

 only of the so-called vesicle of Purkinje, and that all the other 

 parts are accessory, superimposed and unessential. In particular 

 that the yellow yolk of the bird and scaly reptile is analogous to 

 the corpus luteum of the human ovary '' [!], &c. 



Prof. Allen Thomson seems to think, with H. Meckel, that 

 the zona pellucida in Birds disappears, that the "yellow yolk'' is 

 then added, and that around the yellow yolk a membrane is 

 afterwards formed, which is the vitelline membrane of the Bird's 

 laid e^^. I have entered upon no renewed inquiries with the 

 microscope upon this subject, but must say that I did not 

 observe any such disappearance of the original zona in the ova- 

 rian ovum of the Bird, and have always considered the vitellary 

 membrane of its laid e^^ to be the original one in a distended 

 state, it having imbibed the material for the superadded true 

 yellow yolk. 



XXXVIII. Some account of the Discoveries of Keber on the 

 Porosity of Bodies ; with Confirmations. By Martin Barry, 

 M.D., F.RS.^ 



AFTER reading the work of Keber on the porosity of 

 bodies, a copy of which the author was so good as to 

 send me immediately after its publication, I felt that English 

 physiologists would be glad to see an account of the same, and 

 thus be afforded an opportunity of testing the observations it 

 records. I therefore wrote to Dr. Keber, stating, that if he 

 were inclined to send me a short abstract of the work, I would, 

 my health permitting, translate and send it to one of our 

 journals. The following is the result — in communicating which 

 t have the satisfaction of knowing it to be the opinion of the 

 illustrious Owen, that the said work has " peculiar value," from 

 its indefatigable author having devoted his skill " to a depart- 

 ment of research of prime influence at the actual phase of the 

 physiology of tissues." 



Microscopic Researches on the Porosity of Bodies. 

 By F. Keber. 

 " Under this title I have recently published a paperf contain- 

 ing the results of microscopic researches continued for months. 



* Communicated by the Author. 



t F. Keber, Microscopische Untersuchungen iiber die Torositdi der 

 Korper. Nehst einer Abhandlung uber den Eintritt der Samenzellen in 

 das Ei. Mit Zusatzen von M. Barry. Konigsberg, 1854. 



