STEUCTURE OF LIMULUS HEART MUSCLE. 



WALTIOR J. MEEK.^ 



Since the physiology of the Limiilus heart has been so carefully 

 investigated and that organ has been used so successfully in attacking 

 many physiological problems, it has seemed desirable that something 

 should be known concerning its histology. The chief objection to 

 applying any of the results obtained on this form to the vertebrate 

 heart has been that Limulus is a representative of a group unique 

 in the animal kingdom and well removed even from its nearest rela- 

 tives. This fact makes it all the more desirable to investigate the 

 heart musculature in this form and to find what similarity, if any, 

 it bears to the vertebrate type. 



Material and Technique. 



Heart tissue from adult Limuli was used. The most of the mate- 

 rial was prepared at Wood's Hole where fresh tissue was also exam- 

 ined. The hearts from some animals that had been shipped to Chi- 

 cago were also used. These animals were in good condition and noth- 

 ing atypical was found in the tissues. 



A number of fixatives were used, including Carnoy's solution, 

 Perenyi's fluid, acetic-sublimate, and Zenker's solution. Of these 

 Zenker's proved by far the most serviceable and satisfactory. The 

 hearts were split open, washed in sea water to free them from blood 



'I take pleasiu-e in thanking the Marine Biological Laboratory for material 

 and also Dr. Rardeen and Dr. Erlanger, of the University of Wisconsin, for 

 technical assistance. IMy thanks are also dne Dr. Carlson, of the University 

 of riiicago. for advice concerning the work. 



The .luiKNAr, ok Mi(i!rn<>l-0(iv. — Vol. XX, No. 3. 



