this photo is the one i was searching for. the book says this about it:
Enema among the Banziri (in what is now the Central African Republic) - Collection L. Martin
Instillation or insufflation of enema liquids into small children is a common type of self-care in sub-Saharan Africa, particularly for young children. modern estimates suggest that at least one million enemas are being used every month is Soweto and that infants in Swaziland may receive as many as 50 enemas a year.
if you know of any other websites that feature vintage photos of indigenous people, feel free to share.