The first analyses of marsupial milk were reported by Bolliger and Pascoe (1953). However, only eight specimens from three kangaroos (Macropus robustus) with large young could be examined, and it was obvious that further data were required from this or some other marsupial to gain more insight into the chemical composition of the milk of metatheria with their unique second extrauterine period of gestation in a pouch formed by skin. At the suggestion of Dr. Ethel C. Dunham, the milk of a smaller marsupial (Trichosurus vulpecula), the common brush-tail phalanger, or Australian opossum, was examined.
Remarks on Suckling and Collection of Milk Samples
After a short period of gestation of about 20 days, the female of T. vulpecula with a body weight of 1.5-2.0 kg. delivers a single offspring, which immediately after birth proceeds to the pouch. In the newly born "pouch embryo," which measures about 1.5 cm. in length
R. GROSS, A. BOLLIGER. Composition of Milk of the Marsupial Trichosurus Vulpecula. AMA Am J Dis Child. 1959;98(6):768–775. doi:10.1001/archpedi.1959.02070020770013