THE LYMPHATIC SYSTEM. 175 



TJie subarachnoid and subdural lymph-spaces and their 

 prolongations. Axel Key and Retzius have shown that be- 

 sides the great subarachnoid and subdural lymph-spaces of 

 the brain and spinal cord, connecting with them are spaces en- 

 closing the nerve-fibres of the cord, and, what is still more 

 remarkable, extending outward on the peripheral nerves. The 

 nerves of special sense, the olfactory, the optic, and the audi- 

 tory, form no exception to this rule. Even the ganglia of the 

 sj^mpathetic system and their fibres have similar spaces, which 

 are in connection with the cord. Nor is this the end of the 

 intricate labyrinth. Each nerve-fibre has a space immediately 

 outside of the sheath of Schwann, between the latter and the 

 so-called fibrillary sheath, through which it communicates with 

 the perineural sheath-space, and through the latter with the 

 lymph -spaces of the central nervous system. That they are 

 true lymphatic spaces is shown by the fact that they are lined 

 by a layer of endothelial cells. Obersteiner demonstrated by 

 injections that the nerve-cells also possess pericellular spaces 

 connected with those of the corresponding fibres, a fact which 

 I can corroborate. Key and Retzius say that this whole lym- 

 phatic system is nowhere in direct communication with the 

 ordinary lymphatic system, and that they have never seen the 

 latter injected through the former, except when extravasation 

 occurred. Bogras was the first (1825) to inject the nerves. He 

 used quicksilver, and succeeded in injecting the peripheral 

 nerves up to the ganglia, and made injections from the dura 

 down to the ganglia. He failed with the olfactory, optic, and 

 acoustic. Cruveilhier, and later, Robin, confirmed the fact 

 that such injections are possible. Robin, in 1858, and after- 

 ward, His, in 1863, demonstrated the perivascular lymph- 

 spaces of the central nervous system. 



Lymphatics of tendons. Axel Key and Retzius, and also 

 Hertzog, have shown that the tendons possess spaces which 

 may be injected. From the spaces formed by the endotenium 

 and the peritenium, which communicate, connections exist 

 with the deep and superficial lymphatics of the tendon. 



The development of the lymphatics is by a process of bud- 

 ding and vacuolation similar to that which takes place in the 

 blood-vessels. 



Lymphatic glands. We now pass to the consideration of 

 the lymphatic bodies called glands^ ganglia^ or nodes. Their 



