These devices are often about the size of a deck of cards. They hold the drug supply, a mechanism for
  injecting it slowly and smoothly into an attached catheter , a battery to power the mechanism and controls for
  regulating the rate of drug delivery. Many of the pumps have become very sophisticated. Some have alarms to
  alert you to problems. One of the newer systems can deliver four separate drugs in a preset time sequence.
      Several types are available. The balloon pump (Travenol infuser) is the cheapest and simplest, consisting
  basically of a large plastic reservoir. The pump is filled, then attached to a port or catheter. The pump empties
  automatically when it's connected. 
• Central nervous system delivery  Some patients, such as those with acute leukemia, need chemotherapy
  drugs injected into the spinal fluid. This can be done by repeated lumbar punctures (spinal taps), but the
  preferred  method is to use an Ommaya reservoir. This is a rubber bulb usually placed under the scalp. A tiny
  tube connects the reservoir to the spinal fluid compartment. This requires a minor operation for placement of
  the reservoir and tube. Drugs are injected through the skin into the reservoir. Infection in the reservoir area is a
  possibility, so patients are usually monitored for side effects such as tenderness, inflammation , fever, stiff
  neck and headaches.
• Intraperitoneal  This technique which involves delivering drugs directly into the abdominal cavity is
  sometimes used for ovarian or abdominal metastatic cancer. A catheter is connected to a chamber, usually on
  the chest or abdominal wall. The drugs are injected into the chamber, which releases them into the abdominal
  cavity. This eliminates the need to put a new tube into the abdomen every time drugs have to be given. High
  dosages can be given this way, higher than would be possible with any other method of delivery.