4 JacksoTi's Dissection of 



layer passing in an opposite direction, besides some irregular 

 fibres which would give a rotatory movement to the contents. 

 The most efficient muscular power, however, was a large, 

 thick band in the posterior parietes ; it was eighteen inches 

 in length, arose near the cardiac orifice, around which it 

 communicated with the small band which went to the sec- 

 ond cavity, and was at this part six inches broad ; at the 

 thickest part, midway, it was an inch and a quarter in width, 

 and at the further extremity it became broader, thinner, 

 and was gradually lost in the parietes. 



The cells in the first cavity, which serve the animal as a 

 reservoir for water, were arranged in two rows. The first 

 extended fifteen inches from the orifice of the second cavity, 

 along the posterior parietes, towards the left side. Ten trans- 

 verse and parallel septa were sent off at a right angle from 

 the strong muscular band, varying in length from five to 

 nine inches, and in depth from three-fourths to more than 

 two inches, but becoming less and less marked towards the 

 left side, where they gradually disappear. These septa are 

 intersected by others which are thinner, for the most part 

 quite regular, and situated about one inch apart, thus forming 

 the cells which, by estimate, would hold generally from one 

 to four ounces ; at the left extremity, where these last septa 

 are most deficient, the cells are very large, one of them 

 measuring five and a half by two inches, and being capable 

 of holding not far from three or four gills. The first named 

 transverse septa are from two to four lines thick on their 

 free edge, in which are seen well developed muscular fibres 

 arising directly from the large band in the posterior parie- 

 tes of the organ, though less strongly marked than they are 

 represented by Sir E. Home (Comp. Anat. pi. 25) ; his fig- 

 ure, however, was teiken from the two-humped camel, and 

 not from the dromedary ; the cells, also, are surrounded by a 

 few irregular fibres, which would tend to expel their contents. 

 In order to see the fibres in any part of this cavity, the 

 cutis had to be dissected away. — The second row of cells 

 commenced about opposite the middle of the first row on the 

 right side, and extended thirtyfour inches round towards the 



