404 Walter J. Meek. 



and leucocytes, and then small pieces immersed in the fixative. The 

 usual methods of embedding in paraffin and sectioning were employed. 

 Sections were made from 3 to 6 micra in thickness. 



Several different stains were employed, Init iron hematoxylin fol- 

 lowed by eosin was found to be the best for general study. The com- 

 bination has been used largely by investigators and a comparison 

 with their work therefore becomes easy. Orange G and fuchsin were 

 frequently used as counter stains. In studying connective tissue dis- 

 tribution iron hsematoxylin followed by Van Gieson's picro-fuchsin 

 gave good results. A stain equally good and used with success was 

 Mallory's connective tissue stain. Vanadium hsematoxylin was also 

 used in an attempt to demonstrate a sarcolemma. Fresh material was 

 also treated with silver nitrate. 



Fresh material was teased and studied in sea water or salt solu- 

 tion. Fresh tissue was also macerated in 20 per cent nitric acid, 

 40 per cent potassium hydroxide, oO per cent alcohol, and saturated 

 ammonium carbonate, l^itric acid is especially good as a macerating 

 agent, since the preparation may be washed, passed into glycerine, 

 and preserved. Material fixed in Zenker's solution and preserved in 

 70 per cent alcohol was also found to tease easily. These prepara- 

 tions could be stained with htematoxylin and eosin and then showed 

 nearly all the details clearly. 



General Mokphology. 

 The heart of Limidus is a hollow sack 15-20 centimeters long and 

 1.5-3 centimeters wide. It is swung in the pericardial sinus by 

 eight pairs of connecti^'e tissue ligaments, the alary muscles, which 

 form a lateral support for the heart and extend to the pericardium 

 with which they fuse. On its dorsal surface the heart has eight 

 pairs of ostia. The ostia are narrow slits connecting the i)ericardial 

 cavity with the lumen of the heart, and they are supplied with inward 

 projecting connective tissue lips which make efficient valves. Leav- 

 ing the organ are eleven arteries; four pairs of lateral arteries from 

 the four anterior segments, two aortic arches, and one median aorta. 

 The aortic end of the heart is provided with a strong connective 

 tissue valve around which the heart musculature curves concavely 



