EIGHTH ANNUAL REPORT. 51 



The question of the necessity of mechanical or forced-draft sys- 

 tem for this building may be considered settled by conclusive 

 evidence that it is not necessary. The supply of outside air 

 that is continually brought into the building, warmed over coils 

 of hot-water pipes, and delivered both into the large cages and the 

 auditorium, finds its way out of the top of the cages and the 

 main hall by a system of upper currents, which carries away what 

 would otherwise be objectionable animal odors. 



The great decrease in the number of cases of tuberculosis 

 among the primates may fairly be regarded as evidence that the 

 air supply of the Primates' House is very nearly what it should be. 

 During the year 1902, and immediately following the opening of 

 this building, the animals within it were subject to the conditions 

 under which they entered it, and the death-rate from tuberculosis 

 was as heavy as it usually is in such collections. During the first 

 year of the building's use, the animals which entered the Pri- 

 mates' House with tuberculosis disappeared by death, and were re- 

 placed by healthy animals. The mortality records of 1903 show 

 a decrease in the death-rate of the primates of nearly fifty per 

 cent., bringing the total for the year down to a comparatively 

 small number. 



In Europe it is a common practice to keep all orangs and 

 chimpanzees behind glass. Our policy has been to keep nothing, 

 save marmosets, behind glass, and to give the anthropoid apes 

 as much fresh air as they can stand without contracting severe 

 colds. In fact, in comparison with the views of some European 

 authorities respecting the air supply of anthropoid apes, we have 

 gone to the opposite extreme, and prefer to furnish to the orangs 

 and chimpanzees a supply of air so cool and fresh that occasion- 

 ally it produces a head cold, rather than weaken the lungs of 

 those creatures by a constant high temperature, and consequent 

 diminution of vitality. 



All the large cages of the Primates' House have proven con- 

 ducive to great activity on the part of their living inhabitants. 

 The only cases of cage paralysis (three in number) have occurred 

 in the small side cages. It must be borne in mind, however, that 

 in every large collection of primates there must be a liberal num- 

 ber of small cages for the use of timid animals that fare badly in 

 mixed company, and also for quarrelsome individuals that will 

 not live peaceably in the cages that are devoted to groups. 



The lignolith floors of our cages have proven of extreme value 

 in the matter of cleanliness, and the manner in which that mate- 

 rial has been applied to connect the floor with the lower portions. 



