GALEN. 55 



intestines themselves. Some of Galen's contemporaries 

 asserted that upon exposing the mesentery of a sucking 

 animal several small vessels were seen filled first with 

 air, and afterwards with milk. They had, doubtless, 

 mistaken colourless lymph for air; but Galen ridicules 

 both assertions, and thereby shows that he had not 

 examined the contents of the lacteals. This is some- 

 what remarkable, because as a rule he omitted no oppor- 

 tunity of determining with certainty, by vivisection and 

 experiments on living animals, the uses of the various 

 parts of the body. As an illustration of this, we have 

 his correct statement, established by experiment, that 

 the pylorus acts as a valve only during the process of 

 digestion, and that it is relaxed when digestion is com- 

 pleted. 



He recognizes that the flesh of the heart is somewhat 

 different to that of the muscles of voluntary motion. Its 

 fibres are described as being arranged in longitudinal 

 and transverse bundles ; the former by their contractions 

 shortening the organ, the latter compressing and narrow- 

 ing it. Such statements show that he regarded the heart 

 as essentially muscular. He thought, however, -that it 

 was entirely destitute of nerves. Although he admitted 

 that possibly it had one small branch derived from the 

 nervus vagus sent to it, yet he entirely overlooked the 

 great nervous plexus surrounding the roots of the blood- 

 vessels, from which branches proceed in company with 



