418 THE AMERICAN MONTHLY [Dec. 



tional to those lUt-iitioiuMl occniiino- a larj^e juirt of the 

 body cavity are »i,-oiiads, aiul do not belong to the al'wneti- 

 tary system, ^Inke a diawiiig to show tliese jioiuts. 

 Then cat off the, oesophagus, also the intestine, and reniov^e 

 the alimentary tube, si)lii open each organ and examine 

 the wall, noting in each an outer inuscidar coat, and an 

 inner shining w?/t'o/AS' coat. It' there are any remains of 

 food in the '^tom.-ich wash them well and examine it" i)Os- 

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

 coats are easier seen if yon soak a j)iece of the wall tirst 

 for a time in 70 i>er cent alcohol. 



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

 alread}' been hx^ated am()n<^ the organs of the body cavity. 

 Examine it carefnily in position, and determine its rela- 

 tions to the adjoining organs and demonstrate as many of 

 the following facts as possible: it lies immediately be- 

 hind the bases of tlie gilh; is ventral to the gullet; is sur- 

 rounded liy a very delicate meml)rane, the i)ericardium, 

 wliich when removed enables yon to see that the organ 

 consists of three portions; the [)ear-shaped ''bulbus ai'tei'- 

 iosus" which runs forward to the gills; ihe thicker walled 

 '^ventricle" directly behind the bulbns; and the thinner 

 walled ''am-icle^" 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 Ciivier, but 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 attachments and 

 immerse it in clean water, cut open its different chambers 

 to see that they are hollow, find if i)0ssible the openings 

 by which the chambers connect; can you find any valoes 

 to guard these openings? 



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

 of Ihe vascular system of a fish without injection, and 

 -especially with a small subject like the smelt which has 

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



