TRANSACTIONS OF THE SECTIONS. 121 



change of gyration, occasioning vibration of the ventricular walls. The 

 second sound is from flapping of the sigmoid valves. 



12. The impulse is partly caused by the progression, partly by at- 

 mospheric pressure, and chiefly by the left ventricle first gyrating into 

 the proper position to do so, carrying the apex against the thorax with 

 a force equal to the diflference of strength between the right and left 

 ventricles. 



13. The pericardium forms a peripherad axis for the motions of the 

 organ. 



On the Functions of the Muscles and Nerves of the Eyeball. By John 

 Walker, Surgeon to the Eye Institution, Manchester. 



The action of the oblique muscles of the eyeball is explained by Mr. 

 Walker as rotating the eye inwards, but by opposite rotatory movements; 

 so that if the eye were rotated in one direction by the action of one of 

 these muscles, it would be returned to its former position by the action 

 of its antagonist ; while, if both muscles were in action together, there 

 would be no rotation at all, but a direct drawing of the eye inwards. 

 An explanation of the reason for the complicated muscular apparatus of 

 the eyeball is afl^orded in Mr. W.'s opinion by a reference to the arrange- 

 ments of the nerves. The distribution of the third nerve to the supe- 

 rior internal and inferior rectus, and to the inferior oblique, points out 

 the association of these muscles in all corresponding motions of both 

 eyes. And the two other nerves (the 4th and 6th) with which the two 

 remaining muscles, viz. the external rectus and superior oblique, are 

 severally supplied, are required for the direction of one eye outwards, 

 while the other is turned inwards, as is the case when even an object is 

 viewed laterally. 



Notice of a newly -discovered Peculiarity in the Structure of the Uterine 

 Decidua, or Decidua Vera. By W. F. Montgomeby, M.D., Pro- 

 fessor of Midwifery to the King and Queen's College of Physicians in 

 Ireland. 



The author confines himself exclusively to a brief notice of a pecu- 

 liarity in the structure of this product ; which, as far as he is aware, 

 has never been described, although perhaps one of its most important 

 and interesting features. 



About four years ago, while preparing the component parts of a 

 human ovum in the third month for lecture, he observed that when the 

 decidua vera was immersed in water, with its uterine surface uppermost, 

 there appeared amongst the floating and shred-like processes which 

 covered it certain small circular openings, which at first he took to be 

 merely foramina in the membrane ; but on attempting to pass the point 

 of a fine glass rod through the opening, he found it to be a cul-de-sac, 

 and being thus incited to ascertain how the matter really was, and ex- 

 amining carefully then, and having repeated the examination frequently 



