Abstract

References
1.
Heath
I D
, (1962 ) Quarterly Journal of Microscopical Science
103 , 457 –475
2.
Keal
E E
, (1971 ) Postgraduate Medical Journal
47 , 171 –177
3.
Lamb
D
Reid
L
, (1969 ) Journal of Pathology
98 , 213 –229
4.
Lamb
D
Reid
L
, (1972 ) British Journal of Diseases of the Chest
66 , 239 , 248
