( 93 ) 



wall of the brain-vesicle. These cells I mean to describe in my 

 second paper. 



Leiden, 25 April '07. 



DESCRIPTION OF FIGURES ON THE PLATE. 



All the figures are magnified 1600 times, and ait- drawn with a camera lucida 

 of Abbe directly after the preparations. Apochrom. oil-immersion lens of Zeiss and 

 compens-ocular No. S. 



Fig. 1. Colossal nerve-cell with neurofibrillar network, of a Branchiostoma of 

 4.8 cM. in length (Bielsc.uowsky— Pollack's method). 

 „ 2. Dendrites of a similar cell of an animal of 5 cM. in length (same method). 

 „ 3. Neurofibrillar network of a colossal nerve-cell of a Branchiostoma of 



6 mlM. in length. 

 , & a and b. Sections of a medium-sized nerve-cell of the same spinal cord 



as fig. -2. 

 , 5. Section of a very small nerve-cell, with neurofibrillar network. 

 , G. The same as in lig. 4. 



, 7. Section of a sensory cell of Pontobdella, ol 10 |U . Ireated after the gold- 

 method of Apathy. 

 8—11. Sections through different cells of the dorsal group of cells lying 

 behind the brain-vesicle, taken from preparations of several adull 

 specimens of Branchiostoma. In fig. 8 some "I the adjoining cells are 

 drawn, to demonstrate the similarity of structure "t' the nuclei in the 

 two cell types. 

 In fig. 10 and fig. 11 me drawn two typical sections through cup-shaped 

 cells of the dorsal group ol' cells. The body contained in the centre 

 of the cell of tig. 11 is the prolongation ol' the glious basket sur- 

 rounding the cell. Compare fig. 10. 



Physiology. - --(hi a third heart sound". By W. Einthoven, in 

 collaboration with Messrs. .1. H. Wierinoa and E. P. Snijders, 

 assistents at the physiological laboratory at Leyden. 



When continuing the investigation ol' the hearl sounds by means 



of the string galvanometer l ), we noticed that in some cardiopl - 



grams, especially with the apex si ds of W i. recorded in February 



last, shortly after the vibrations of the second sound still another 

 vibration was present, which admitted ol' no other interpretation than 

 by regarding it as a third hearl sound. 



We could not at once explain how this third sound was produced, 

 and we put oil' the closer investigation of' this phenomenon, however 



!) See: Die Registrirung der menschlichen Herztöue miltels des Saitengalvano- 

 meters. Pflüger's Arch. I', d. gesammte Physiol. Vol. 117, p. 461, 1907. 



ti* 



