The lumbrical muscles do not attach to the proximal phalanx directly, but rather connect the tendons of flexor digitorum profundus (below, ie volar) to the extensor tendons (above, ie dorsal) and produce flexion by pulling on the extensor tendons as they pass over the proximal phalanx.
By the time they are 12 months old, most babies can weigh three times what they weighed at birth and gain about an inch per month in length. The average infant at one year may be between 2630 inches long. Social and Emotional Development-Infants respond when you say their name. They begin to fear strangers.
By 4 months babies are able to grasp and hold large objects such as blocks, but they are still not able to grasp small things such as peas. Between 4 and 7 months, babies start picking up things and put them in their mouth. Babies, who are eating solids by now, will try to hold a baby spoon.