Scientific Proceedings. (203) 33 



II. Conduction in the Heart in the State of Water-Rigor. — 

 The experiments of Fredericq, Waller and Reid, Bayliss and Star- 

 ling, Schliiter, Engelmann, Hofmann, and Bethe have shown that 

 the heart walls may conduct without contracting or being able to 

 contract. This can be interpreted in two ways, viz. : (1) The con- 

 duction takes place in the nervous tissue, or (2) the conduction 

 takes place in the muscular tissue, but the processes of conduction 

 and contraction are so independent of one another that the muscle 

 may conduct without contracting. The latter is the explanation 

 usually adopted, based on the experiments of Biedermann and 

 Engelmann on conduction in muscle in the state of water-rigor. 

 Engelmann, worked on the frog's heart. In the heart of Limulus 

 the above two possible explanations may be put to experimental 

 test. 



The author transected the heart-muscle in the region of the 

 second and the fourth heart-segments and dissected away a por- 

 tion of the muscle about 0.5 cm. in length, leaving the three 

 portions of the heart connected alone by the nerve-plexus (the 

 median nerve-cord and the lateral nerves). The anterior and 

 the middle portions of the heart continued in rhythm by virtue of 

 the impulses from the ganglion of the posterior portion, these im- 

 pulses reaching the two anterior portions by means of the intact 

 nerve-plexus. When this nervous plexus is severed in the fourth 

 segment, the region of the heart anterior to the sections ceases 

 to beat. Hence, the anterior portion of the heart thus prepared 

 beats in response to impulses that reach it through the nerve- 

 plexus on the middle portion. Now, when this middle portion of 

 the heart is placed in water, the muscle of this region absorbs 

 water and ceases to beat or respond to artificial stimulation, while 

 the anterior portion still beats in synchrony with the posterior 

 portion of the heart. The nerves will also lose their conductivity 

 if left in the water long enough. On replacing the water by plasma 

 or sea-water the nerves are quickly restored. The muscle is re- 

 stored very slowly and sometimes not at all. The nerve-plexus 

 in the Limulus heart is composed of nonmedullated nerves, just 

 as is the intramuscular nerve-plexus in the heart of a vertebrate. 

 Now, since the behavior of the Limulus heart and the heart of a 

 vertebrate in the state of water-rigor is the same, and, further, as 



