Abstract

References
1.
Davis
J M
(1961 ) Postgrad. med. J . 37 , 783
2.
Lockhart-Mummery
H E
&
Morson
B C
(1960 ) Gut
1 , 87
3.
Morson
B C
&
Lockhart-Mummery
H E
(1959 ) Lancet
ii , 1122
4.
Parks
A G
&
Couch
R S C
(1962 ) Lancet
i , 136
