Henry L. Bruner 73 
of the heart, which thus augments all of the processes named above. 
Vaso-motor adjustments probably produce like effects. The general re- 
sult is more or less evident swelling of the soft parts of the head, which 
reaches its maximum in the orbital region where the enlargement is 
facilitated by relaxation of the orbital muscles. At the end of this stage, 
under ordinary conditions, a maximum enlargement is reached, which 
indicates that the distension of veins has attained its limit under the 
existing arterial pressure. 
II. Second stage of intumescence. 
3. Contraction of m. protrusor oculi, m. temporalis, and the bucco- 
pharyngeal muscles. During this stage the m. constrictor ven jugularis 
interne maintains its tonus and the venous blood-pressure is raised to a 
higher level. In the anterior part of the head this is due especially to 
the action of the m. protrusor oculi and m. temporalis, which press 
upon the flooded sinus orbitalis and thus send a wave of high pressure 
through the anterior veins. <A similar elevation of blood-pressure occurs 
also in the posterior part of the head, where it is probably caused by the 
combined action of all of the muscles mentioned above. External evi- 
dence of the higher blood-pressure is most plainly visible in the orbital 
region, where the protrusion is greatly increased. A pulse-like movement 
ray also occur at the external naris, where it is caused by the disten- 
sion of the sinus vestibuli nasi. 
III. Stage of reduction. 
4. Relaxation of the m. constrictor vene jugularis interne, m. protru- 
sor oculi and bucco-pharyngeal muscles; contraction of the muscles of the 
orbit; reduction of the flooded veins and sinuses. 
5. The decline of blood-pressure is followed by a slowing down of the 
heart-beat, probably also by vaso-motor changes which aid in restoring 
the circulation to its normal condition. 
The foregoing events form a normal cycle of intumescence. This is 
the usual process, which includes two well-marked stages. An incom- 
plete cycle sometimes occurs with omission of the second stage. Occa- 
sionally, also, the movements of the second stage have been observed, 
without any evidence of previous contraction of the m. constrictor ven 
jugularis interne, the result being a moderate protrusion of the eye. 
g. GENERAL REMARKS ON THE DISTENSION OF THE CEPHALIC VEINS 
AND SINUSES OF THE SAURIA. 
1. During the first stage of intumescence, following the contraction of 
the m. constrictor vene jugularis interne, the blood-pressure in the 
cephalic veins and sinuses is modified in a variety of ways. 
