80 1HE SCAFFOLDING LEFT IN THE BODY. 



most prominent feature, indeed, after the head, in 

 svery mammalian embryo, are the four clefts or fur- 

 rows of the old gill-slits. They are still known in 

 Embryology by the old name gill-slits and so per- 

 sistent are these characters that children are known 

 to have been born with them not only externally 

 visible which is a common occurrence but open 

 through and through, so that fluids taken in at the 

 mouth could pass through and trickle out at the neck. 

 This last fact was so astounding as to be for a long 

 time denied. It was thought that, when this hap- 

 pened, the orifice must have been accidentally made 

 by the probe of the surgeon. But Dr. Button has 

 recently met with actual cases where this has 

 occurred. " I have seen milk," he says, " issue from 

 such fistulse in individuals who have never been 

 submitted to sounding." 1 In the common case of 

 children born with these vestiges, the old gill-slits are 

 represented by small openings in the skin on the sides 

 of the neck, and capable of admitting a thin probe. 

 Sometimes even the place where they have been in 

 childhood is marked throughout life by small round 

 patches of white skin. 



Almost more astonishing than the fact of their 

 persistence is the use to which Nature afterwards put 

 them. When the fish came ashore, its water-breath- 

 ing apparatus was no longer of any use to it. At first 

 it had to keep it on, for it took a long time to perfect 

 the air-breathing apparatus destined to replace it. 

 But when this was ready the problem arose, What 

 was to be done with the earlier organ ? Nature is 



1 Evolution and Disease, p. 81. 



