418 THE AMERICAN MONTHLY [Dec. 



tional to tliose mentioned occui)ing a lar<j:;e ]>?irt of tlie 

 •body cavity are gonads, and do not belong to the alimen- 

 tary system. Make a drawing to sliow tliese points. 

 Then cut off the oesophagus, also the intestine, and rem )ve 

 Ihe alimentary tube, split open each organ and ex.'imiiie 

 the wjili, noting in each an outer muscular coat, find an 

 inner shining mucous coat. If there are any remains of 

 food in the stomach wash them well and examine if pos- 

 sible tlie nature of the food on which the tish fed. The 

 coats are easier seen if you soak a piece of the wall ti'ist 

 for a time in 70 per cent alcohol. 



10. The Heart and Blood-Vessels. — The heart has 

 already been located among the organs of the hody cavity. 

 Examine it carefully in position, and determine its rela- 

 tions to the adjoining organs and demonstrate as many of 

 the following facts as possible: it lies immediately lie- 

 hind the bases of the gills; is ventral to the gullet; is siir- 

 Tounded by a very delicate membrane, the pericardium, 

 which when removed enables you to see that the organ 

 consists of three portions: the pear-shaped ''bulbus arter- 

 iosus,'' which runs forward to the gills; the thicker walled 

 ^^ventricle" directly behind the bulbus; and the thinner 

 walled ''a?^ricZe," larger than the ventricle dorsal to it 

 and overlapping it on both sides. (There are vessels 

 which bring blood into the auricle from either side, ducts 

 of Cuvier, hut they are not easily demonstrated on the 

 smelt and there is a vein coming from the liver, hepatic 

 vein). Cut the heart away from its Httachment;:^ and 

 immerse it in clean water, cut open its different chambers 

 to see that they are hollow, find if possible the openings 

 by which the chambers connect; can you find any valoes 

 to guard these openings? 



[It is not possible to do very much with the dissection 

 of the vascular system of a fish without injection, and 

 -especially with a small subject like the smelt which has 

 been dead for severel days (or weeks). However the 



