96 THE DUCTLESS GLANDS 



form of cell, which categories are homologous with the two 

 constituents of the adrenals of higher vertebrates. 



In Amphioxus nothing corresponding to the adrenals has so 

 far been discovered, and in the Invertebrata the matter may 

 perhaps be considered somewhat doubtful. 



2. Invertebrata 



Leydig discusses the possibility of the existence in some 

 Invertebrata of the equivalents of the adrenal bodies. 



Some years ago the present writer had considered the possi- 

 bility of the existence of the representatives of cortex and 

 medulla of the adrenal bodies in the Invertebrata, but had not 

 succeeded in finding any organs or tissues which seemed at all 

 likely to correspond to them. But just previously to that time 

 physiological research had rendered it possible to test any 

 unknown organ or tissue to see if it should be homologous with 

 adrenal medulla. An extract made from the medulla of the 

 adrenal or from any (chromaphil) tissue of the same nature 

 possesses powerful pressor properties. 



Accordingly an extract from certain tissues (including the 

 cells which Leydig thought might correspond to the adrenal 

 bodies of vertebrates) of Paludina vivipara was prepared and 

 injected into the venous system of a cat. The result was 

 negative, possibly because the material necessarily contained 

 so much nervpus tissue which would tend to lower the blood- 

 pressure. Cleghorn finds that glycerin and saline extracts of 

 sympathetic ganglia produce a fall of blood-pressure, in spite 

 of the presence in these ganglia of chromaphil cells like those 

 in the medulla of the adrenal body. l It appears, also, that it 

 is impossible to obtain any rise of blood-pressure by injecting 

 extracts of carotid glands into an animal, because there is so 

 much admixture with various tissues whose extracts have a 

 depressor effect. 



Poll and Summer describe certain cells in the abdominal 

 ganglia of Hirudo medicinalis which stain a yellowish-brown 

 with Miiller's fluid. They consider it probable that these are 

 h<mi< riotous with the chromaphil cells discovered by Stilling. 



honi did not ascertain that this result might be obtained from ;my 

 nervous ti-^u.\ \\ln-tln-r Inain, spinal cord, or peripheral nerve: in t'.-n-t. In- 

 states that this is not the case. 



